654 lines
23 KiB
C
654 lines
23 KiB
C
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// Copyright 2018 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// -----------------------------------------------------------------------------
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// File: btree_set.h
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// -----------------------------------------------------------------------------
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//
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// This header file defines B-tree sets: sorted associative containers of
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// values.
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//
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// * `absl::btree_set<>`
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// * `absl::btree_multiset<>`
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//
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// These B-tree types are similar to the corresponding types in the STL
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// (`std::set` and `std::multiset`) and generally conform to the STL interfaces
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// of those types. However, because they are implemented using B-trees, they
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// are more efficient in most situations.
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//
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// Unlike `std::set` and `std::multiset`, which are commonly implemented using
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// red-black tree nodes, B-tree sets use more generic B-tree nodes able to hold
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// multiple values per node. Holding multiple values per node often makes
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// B-tree sets perform better than their `std::set` counterparts, because
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// multiple entries can be checked within the same cache hit.
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//
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// However, these types should not be considered drop-in replacements for
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// `std::set` and `std::multiset` as there are some API differences, which are
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// noted in this header file.
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//
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// Importantly, insertions and deletions may invalidate outstanding iterators,
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// pointers, and references to elements. Such invalidations are typically only
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// an issue if insertion and deletion operations are interleaved with the use of
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// more than one iterator, pointer, or reference simultaneously. For this
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// reason, `insert()` and `erase()` return a valid iterator at the current
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// position.
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#ifndef ABSL_CONTAINER_BTREE_SET_H_
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#define ABSL_CONTAINER_BTREE_SET_H_
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#include "absl/container/internal/btree.h" // IWYU pragma: export
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#include "absl/container/internal/btree_container.h" // IWYU pragma: export
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namespace absl {
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// absl::btree_set<>
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//
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// An `absl::btree_set<K>` is an ordered associative container of unique key
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// values designed to be a more efficient replacement for `std::set` (in most
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// cases).
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//
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// Keys are sorted using an (optional) comparison function, which defaults to
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// `std::less<K>`.
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//
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// An `absl::btree_set<K>` uses a default allocator of `std::allocator<K>` to
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// allocate (and deallocate) nodes, and construct and destruct values within
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// those nodes. You may instead specify a custom allocator `A` (which in turn
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// requires specifying a custom comparator `C`) as in
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// `absl::btree_set<K, C, A>`.
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//
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template <typename Key, typename Compare = std::less<Key>,
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typename Alloc = std::allocator<Key>>
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class btree_set
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: public container_internal::btree_set_container<
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container_internal::btree<container_internal::set_params<
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Key, Compare, Alloc, /*TargetNodeSize=*/256,
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/*Multi=*/false>>> {
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using Base = typename btree_set::btree_set_container;
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public:
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// Constructors and Assignment Operators
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//
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// A `btree_set` supports the same overload set as `std::set`
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// for construction and assignment:
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//
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// * Default constructor
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//
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// absl::btree_set<std::string> set1;
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//
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// * Initializer List constructor
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//
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// absl::btree_set<std::string> set2 =
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// {{"huey"}, {"dewey"}, {"louie"},};
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//
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// * Copy constructor
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//
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// absl::btree_set<std::string> set3(set2);
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//
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// * Copy assignment operator
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//
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// absl::btree_set<std::string> set4;
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// set4 = set3;
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//
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// * Move constructor
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//
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// // Move is guaranteed efficient
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// absl::btree_set<std::string> set5(std::move(set4));
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//
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// * Move assignment operator
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//
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// // May be efficient if allocators are compatible
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// absl::btree_set<std::string> set6;
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// set6 = std::move(set5);
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//
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// * Range constructor
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//
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// std::vector<std::string> v = {"a", "b"};
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// absl::btree_set<std::string> set7(v.begin(), v.end());
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btree_set() {}
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using Base::Base;
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// btree_set::begin()
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//
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// Returns an iterator to the beginning of the `btree_set`.
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using Base::begin;
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// btree_set::cbegin()
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//
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// Returns a const iterator to the beginning of the `btree_set`.
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using Base::cbegin;
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// btree_set::end()
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//
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// Returns an iterator to the end of the `btree_set`.
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using Base::end;
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// btree_set::cend()
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//
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// Returns a const iterator to the end of the `btree_set`.
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using Base::cend;
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// btree_set::empty()
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//
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// Returns whether or not the `btree_set` is empty.
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using Base::empty;
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// btree_set::max_size()
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//
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// Returns the largest theoretical possible number of elements within a
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// `btree_set` under current memory constraints. This value can be thought
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// of as the largest value of `std::distance(begin(), end())` for a
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// `btree_set<Key>`.
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using Base::max_size;
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// btree_set::size()
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//
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// Returns the number of elements currently within the `btree_set`.
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using Base::size;
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// btree_set::clear()
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//
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// Removes all elements from the `btree_set`. Invalidates any references,
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// pointers, or iterators referring to contained elements.
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using Base::clear;
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// btree_set::erase()
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//
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// Erases elements within the `btree_set`. Overloads are listed below.
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//
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// iterator erase(iterator position):
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// iterator erase(const_iterator position):
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//
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// Erases the element at `position` of the `btree_set`, returning
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// the iterator pointing to the element after the one that was erased
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// (or end() if none exists).
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//
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// iterator erase(const_iterator first, const_iterator last):
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//
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// Erases the elements in the open interval [`first`, `last`), returning
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// the iterator pointing to the element after the interval that was erased
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// (or end() if none exists).
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//
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// template <typename K> size_type erase(const K& key):
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//
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// Erases the element with the matching key, if it exists, returning the
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// number of elements erased.
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using Base::erase;
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// btree_set::insert()
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//
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// Inserts an element of the specified value into the `btree_set`,
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// returning an iterator pointing to the newly inserted element, provided that
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// an element with the given key does not already exist. If an insertion
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// occurs, any references, pointers, or iterators are invalidated.
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// Overloads are listed below.
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//
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// std::pair<iterator,bool> insert(const value_type& value):
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//
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// Inserts a value into the `btree_set`. Returns a pair consisting of an
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// iterator to the inserted element (or to the element that prevented the
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// insertion) and a bool denoting whether the insertion took place.
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//
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// std::pair<iterator,bool> insert(value_type&& value):
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//
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// Inserts a moveable value into the `btree_set`. Returns a pair
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// consisting of an iterator to the inserted element (or to the element that
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// prevented the insertion) and a bool denoting whether the insertion took
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// place.
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//
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// iterator insert(const_iterator hint, const value_type& value):
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// iterator insert(const_iterator hint, value_type&& value):
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//
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// Inserts a value, using the position of `hint` as a non-binding suggestion
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// for where to begin the insertion search. Returns an iterator to the
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// inserted element, or to the existing element that prevented the
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// insertion.
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//
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// void insert(InputIterator first, InputIterator last):
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//
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// Inserts a range of values [`first`, `last`).
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//
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// void insert(std::initializer_list<init_type> ilist):
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//
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// Inserts the elements within the initializer list `ilist`.
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using Base::insert;
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// btree_set::emplace()
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//
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// Inserts an element of the specified value by constructing it in-place
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// within the `btree_set`, provided that no element with the given key
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// already exists.
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//
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// The element may be constructed even if there already is an element with the
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// key in the container, in which case the newly constructed element will be
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// destroyed immediately.
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//
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// If an insertion occurs, any references, pointers, or iterators are
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// invalidated.
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using Base::emplace;
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// btree_set::emplace_hint()
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//
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// Inserts an element of the specified value by constructing it in-place
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// within the `btree_set`, using the position of `hint` as a non-binding
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// suggestion for where to begin the insertion search, and only inserts
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// provided that no element with the given key already exists.
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//
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// The element may be constructed even if there already is an element with the
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// key in the container, in which case the newly constructed element will be
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// destroyed immediately.
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//
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// If an insertion occurs, any references, pointers, or iterators are
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// invalidated.
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using Base::emplace_hint;
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// btree_set::extract()
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//
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// Extracts the indicated element, erasing it in the process, and returns it
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// as a C++17-compatible node handle. Overloads are listed below.
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//
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// node_type extract(const_iterator position):
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//
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// Extracts the element at the indicated position and returns a node handle
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// owning that extracted data.
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//
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// template <typename K> node_type extract(const K& x):
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//
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// Extracts the element with the key matching the passed key value and
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// returns a node handle owning that extracted data. If the `btree_set`
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// does not contain an element with a matching key, this function returns an
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// empty node handle.
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//
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// NOTE: In this context, `node_type` refers to the C++17 concept of a
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// move-only type that owns and provides access to the elements in associative
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// containers (https://en.cppreference.com/w/cpp/container/node_handle).
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// It does NOT refer to the data layout of the underlying btree.
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using Base::extract;
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// btree_set::merge()
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//
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// Extracts elements from a given `source` btree_set into this
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// `btree_set`. If the destination `btree_set` already contains an
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// element with an equivalent key, that element is not extracted.
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using Base::merge;
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// btree_set::swap(btree_set& other)
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//
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// Exchanges the contents of this `btree_set` with those of the `other`
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// btree_set, avoiding invocation of any move, copy, or swap operations on
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// individual elements.
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//
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// All iterators and references on the `btree_set` remain valid, excepting
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// for the past-the-end iterator, which is invalidated.
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using Base::swap;
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// btree_set::contains()
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//
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// template <typename K> bool contains(const K& key) const:
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//
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// Determines whether an element comparing equal to the given `key` exists
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// within the `btree_set`, returning `true` if so or `false` otherwise.
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//
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// Supports heterogeneous lookup, provided that the set is provided a
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// compatible heterogeneous comparator.
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using Base::contains;
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// btree_set::count()
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//
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// template <typename K> size_type count(const K& key) const:
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//
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// Returns the number of elements comparing equal to the given `key` within
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// the `btree_set`. Note that this function will return either `1` or `0`
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// since duplicate elements are not allowed within a `btree_set`.
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//
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// Supports heterogeneous lookup, provided that the set is provided a
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// compatible heterogeneous comparator.
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using Base::count;
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// btree_set::equal_range()
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//
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// Returns a closed range [first, last], defined by a `std::pair` of two
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// iterators, containing all elements with the passed key in the
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// `btree_set`.
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using Base::equal_range;
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// btree_set::find()
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//
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// template <typename K> iterator find(const K& key):
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// template <typename K> const_iterator find(const K& key) const:
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//
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// Finds an element with the passed `key` within the `btree_set`.
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//
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// Supports heterogeneous lookup, provided that the set is provided a
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// compatible heterogeneous comparator.
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using Base::find;
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// btree_set::get_allocator()
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//
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// Returns the allocator function associated with this `btree_set`.
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using Base::get_allocator;
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// btree_set::key_comp();
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//
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// Returns the key comparator associated with this `btree_set`.
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using Base::key_comp;
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// btree_set::value_comp();
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//
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// Returns the value comparator associated with this `btree_set`. The keys to
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// sort the elements are the values themselves, therefore `value_comp` and its
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// sibling member function `key_comp` are equivalent.
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using Base::value_comp;
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};
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// absl::swap(absl::btree_set<>, absl::btree_set<>)
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//
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// Swaps the contents of two `absl::btree_set` containers.
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template <typename K, typename C, typename A>
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void swap(btree_set<K, C, A> &x, btree_set<K, C, A> &y) {
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return x.swap(y);
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}
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// absl::btree_multiset<>
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//
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// An `absl::btree_multiset<K>` is an ordered associative container of
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// keys and associated values designed to be a more efficient replacement
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// for `std::multiset` (in most cases). Unlike `absl::btree_set`, a B-tree
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// multiset allows equivalent elements.
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//
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// Keys are sorted using an (optional) comparison function, which defaults to
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// `std::less<K>`.
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//
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// An `absl::btree_multiset<K>` uses a default allocator of `std::allocator<K>`
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// to allocate (and deallocate) nodes, and construct and destruct values within
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// those nodes. You may instead specify a custom allocator `A` (which in turn
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// requires specifying a custom comparator `C`) as in
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// `absl::btree_multiset<K, C, A>`.
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//
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template <typename Key, typename Compare = std::less<Key>,
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typename Alloc = std::allocator<Key>>
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class btree_multiset
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: public container_internal::btree_multiset_container<
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container_internal::btree<container_internal::set_params<
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Key, Compare, Alloc, /*TargetNodeSize=*/256,
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/*Multi=*/true>>> {
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using Base = typename btree_multiset::btree_multiset_container;
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public:
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// Constructors and Assignment Operators
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//
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// A `btree_multiset` supports the same overload set as `std::set`
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// for construction and assignment:
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//
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// * Default constructor
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//
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// absl::btree_multiset<std::string> set1;
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//
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// * Initializer List constructor
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//
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// absl::btree_multiset<std::string> set2 =
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// {{"huey"}, {"dewey"}, {"louie"},};
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//
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// * Copy constructor
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//
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// absl::btree_multiset<std::string> set3(set2);
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//
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// * Copy assignment operator
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//
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// absl::btree_multiset<std::string> set4;
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// set4 = set3;
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//
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// * Move constructor
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//
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// // Move is guaranteed efficient
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// absl::btree_multiset<std::string> set5(std::move(set4));
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//
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// * Move assignment operator
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//
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||
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// // May be efficient if allocators are compatible
|
||
|
// absl::btree_multiset<std::string> set6;
|
||
|
// set6 = std::move(set5);
|
||
|
//
|
||
|
// * Range constructor
|
||
|
//
|
||
|
// std::vector<std::string> v = {"a", "b"};
|
||
|
// absl::btree_multiset<std::string> set7(v.begin(), v.end());
|
||
|
btree_multiset() {}
|
||
|
using Base::Base;
|
||
|
|
||
|
// btree_multiset::begin()
|
||
|
//
|
||
|
// Returns an iterator to the beginning of the `btree_multiset`.
|
||
|
using Base::begin;
|
||
|
|
||
|
// btree_multiset::cbegin()
|
||
|
//
|
||
|
// Returns a const iterator to the beginning of the `btree_multiset`.
|
||
|
using Base::cbegin;
|
||
|
|
||
|
// btree_multiset::end()
|
||
|
//
|
||
|
// Returns an iterator to the end of the `btree_multiset`.
|
||
|
using Base::end;
|
||
|
|
||
|
// btree_multiset::cend()
|
||
|
//
|
||
|
// Returns a const iterator to the end of the `btree_multiset`.
|
||
|
using Base::cend;
|
||
|
|
||
|
// btree_multiset::empty()
|
||
|
//
|
||
|
// Returns whether or not the `btree_multiset` is empty.
|
||
|
using Base::empty;
|
||
|
|
||
|
// btree_multiset::max_size()
|
||
|
//
|
||
|
// Returns the largest theoretical possible number of elements within a
|
||
|
// `btree_multiset` under current memory constraints. This value can be
|
||
|
// thought of as the largest value of `std::distance(begin(), end())` for a
|
||
|
// `btree_multiset<Key>`.
|
||
|
using Base::max_size;
|
||
|
|
||
|
// btree_multiset::size()
|
||
|
//
|
||
|
// Returns the number of elements currently within the `btree_multiset`.
|
||
|
using Base::size;
|
||
|
|
||
|
// btree_multiset::clear()
|
||
|
//
|
||
|
// Removes all elements from the `btree_multiset`. Invalidates any references,
|
||
|
// pointers, or iterators referring to contained elements.
|
||
|
using Base::clear;
|
||
|
|
||
|
// btree_multiset::erase()
|
||
|
//
|
||
|
// Erases elements within the `btree_multiset`. Overloads are listed below.
|
||
|
//
|
||
|
// iterator erase(iterator position):
|
||
|
// iterator erase(const_iterator position):
|
||
|
//
|
||
|
// Erases the element at `position` of the `btree_multiset`, returning
|
||
|
// the iterator pointing to the element after the one that was erased
|
||
|
// (or end() if none exists).
|
||
|
//
|
||
|
// iterator erase(const_iterator first, const_iterator last):
|
||
|
//
|
||
|
// Erases the elements in the open interval [`first`, `last`), returning
|
||
|
// the iterator pointing to the element after the interval that was erased
|
||
|
// (or end() if none exists).
|
||
|
//
|
||
|
// template <typename K> size_type erase(const K& key):
|
||
|
//
|
||
|
// Erases the elements matching the key, if any exist, returning the
|
||
|
// number of elements erased.
|
||
|
using Base::erase;
|
||
|
|
||
|
// btree_multiset::insert()
|
||
|
//
|
||
|
// Inserts an element of the specified value into the `btree_multiset`,
|
||
|
// returning an iterator pointing to the newly inserted element.
|
||
|
// Any references, pointers, or iterators are invalidated. Overloads are
|
||
|
// listed below.
|
||
|
//
|
||
|
// iterator insert(const value_type& value):
|
||
|
//
|
||
|
// Inserts a value into the `btree_multiset`, returning an iterator to the
|
||
|
// inserted element.
|
||
|
//
|
||
|
// iterator insert(value_type&& value):
|
||
|
//
|
||
|
// Inserts a moveable value into the `btree_multiset`, returning an iterator
|
||
|
// to the inserted element.
|
||
|
//
|
||
|
// iterator insert(const_iterator hint, const value_type& value):
|
||
|
// iterator insert(const_iterator hint, value_type&& value):
|
||
|
//
|
||
|
// Inserts a value, using the position of `hint` as a non-binding suggestion
|
||
|
// for where to begin the insertion search. Returns an iterator to the
|
||
|
// inserted element.
|
||
|
//
|
||
|
// void insert(InputIterator first, InputIterator last):
|
||
|
//
|
||
|
// Inserts a range of values [`first`, `last`).
|
||
|
//
|
||
|
// void insert(std::initializer_list<init_type> ilist):
|
||
|
//
|
||
|
// Inserts the elements within the initializer list `ilist`.
|
||
|
using Base::insert;
|
||
|
|
||
|
// btree_multiset::emplace()
|
||
|
//
|
||
|
// Inserts an element of the specified value by constructing it in-place
|
||
|
// within the `btree_multiset`. Any references, pointers, or iterators are
|
||
|
// invalidated.
|
||
|
using Base::emplace;
|
||
|
|
||
|
// btree_multiset::emplace_hint()
|
||
|
//
|
||
|
// Inserts an element of the specified value by constructing it in-place
|
||
|
// within the `btree_multiset`, using the position of `hint` as a non-binding
|
||
|
// suggestion for where to begin the insertion search.
|
||
|
//
|
||
|
// Any references, pointers, or iterators are invalidated.
|
||
|
using Base::emplace_hint;
|
||
|
|
||
|
// btree_multiset::extract()
|
||
|
//
|
||
|
// Extracts the indicated element, erasing it in the process, and returns it
|
||
|
// as a C++17-compatible node handle. Overloads are listed below.
|
||
|
//
|
||
|
// node_type extract(const_iterator position):
|
||
|
//
|
||
|
// Extracts the element at the indicated position and returns a node handle
|
||
|
// owning that extracted data.
|
||
|
//
|
||
|
// template <typename K> node_type extract(const K& x):
|
||
|
//
|
||
|
// Extracts the element with the key matching the passed key value and
|
||
|
// returns a node handle owning that extracted data. If the `btree_multiset`
|
||
|
// does not contain an element with a matching key, this function returns an
|
||
|
// empty node handle.
|
||
|
//
|
||
|
// NOTE: In this context, `node_type` refers to the C++17 concept of a
|
||
|
// move-only type that owns and provides access to the elements in associative
|
||
|
// containers (https://en.cppreference.com/w/cpp/container/node_handle).
|
||
|
// It does NOT refer to the data layout of the underlying btree.
|
||
|
using Base::extract;
|
||
|
|
||
|
// btree_multiset::merge()
|
||
|
//
|
||
|
// Extracts elements from a given `source` btree_multiset into this
|
||
|
// `btree_multiset`. If the destination `btree_multiset` already contains an
|
||
|
// element with an equivalent key, that element is not extracted.
|
||
|
using Base::merge;
|
||
|
|
||
|
// btree_multiset::swap(btree_multiset& other)
|
||
|
//
|
||
|
// Exchanges the contents of this `btree_multiset` with those of the `other`
|
||
|
// btree_multiset, avoiding invocation of any move, copy, or swap operations
|
||
|
// on individual elements.
|
||
|
//
|
||
|
// All iterators and references on the `btree_multiset` remain valid,
|
||
|
// excepting for the past-the-end iterator, which is invalidated.
|
||
|
using Base::swap;
|
||
|
|
||
|
// btree_multiset::contains()
|
||
|
//
|
||
|
// template <typename K> bool contains(const K& key) const:
|
||
|
//
|
||
|
// Determines whether an element comparing equal to the given `key` exists
|
||
|
// within the `btree_multiset`, returning `true` if so or `false` otherwise.
|
||
|
//
|
||
|
// Supports heterogeneous lookup, provided that the set is provided a
|
||
|
// compatible heterogeneous comparator.
|
||
|
using Base::contains;
|
||
|
|
||
|
// btree_multiset::count()
|
||
|
//
|
||
|
// template <typename K> size_type count(const K& key) const:
|
||
|
//
|
||
|
// Returns the number of elements comparing equal to the given `key` within
|
||
|
// the `btree_multiset`.
|
||
|
//
|
||
|
// Supports heterogeneous lookup, provided that the set is provided a
|
||
|
// compatible heterogeneous comparator.
|
||
|
using Base::count;
|
||
|
|
||
|
// btree_multiset::equal_range()
|
||
|
//
|
||
|
// Returns a closed range [first, last], defined by a `std::pair` of two
|
||
|
// iterators, containing all elements with the passed key in the
|
||
|
// `btree_multiset`.
|
||
|
using Base::equal_range;
|
||
|
|
||
|
// btree_multiset::find()
|
||
|
//
|
||
|
// template <typename K> iterator find(const K& key):
|
||
|
// template <typename K> const_iterator find(const K& key) const:
|
||
|
//
|
||
|
// Finds an element with the passed `key` within the `btree_multiset`.
|
||
|
//
|
||
|
// Supports heterogeneous lookup, provided that the set is provided a
|
||
|
// compatible heterogeneous comparator.
|
||
|
using Base::find;
|
||
|
|
||
|
// btree_multiset::get_allocator()
|
||
|
//
|
||
|
// Returns the allocator function associated with this `btree_multiset`.
|
||
|
using Base::get_allocator;
|
||
|
|
||
|
// btree_multiset::key_comp();
|
||
|
//
|
||
|
// Returns the key comparator associated with this `btree_multiset`.
|
||
|
using Base::key_comp;
|
||
|
|
||
|
// btree_multiset::value_comp();
|
||
|
//
|
||
|
// Returns the value comparator associated with this `btree_multiset`. The
|
||
|
// keys to sort the elements are the values themselves, therefore `value_comp`
|
||
|
// and its sibling member function `key_comp` are equivalent.
|
||
|
using Base::value_comp;
|
||
|
};
|
||
|
|
||
|
// absl::swap(absl::btree_multiset<>, absl::btree_multiset<>)
|
||
|
//
|
||
|
// Swaps the contents of two `absl::btree_multiset` containers.
|
||
|
template <typename K, typename C, typename A>
|
||
|
void swap(btree_multiset<K, C, A> &x, btree_multiset<K, C, A> &y) {
|
||
|
return x.swap(y);
|
||
|
}
|
||
|
|
||
|
} // namespace absl
|
||
|
|
||
|
#endif // ABSL_CONTAINER_BTREE_SET_H_
|