124 lines
3.6 KiB
Python
124 lines
3.6 KiB
Python
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import unittest
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from collections import deque
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def is_balanced(node):
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q, seen, ds = deque(), set(), set()
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q.append((0, node))
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while q:
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d, node = q.popleft()
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l, r = node.left, node.right
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seen.add(node)
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if not l and not r:
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if d not in ds and len(ds) == 2:
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return False
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else:
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ds.add(d)
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if l and l not in seen:
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q.append((d + 1, l))
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if r and r not in seen:
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q.append((d + 1, r))
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return max(ds) - min(ds) <= 1
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# Tests
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class Test(unittest.TestCase):
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class BinaryTreeNode(object):
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def __init__(self, value):
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self.value = value
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self.left = None
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self.right = None
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def insert_left(self, value):
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self.left = Test.BinaryTreeNode(value)
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return self.left
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def insert_right(self, value):
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self.right = Test.BinaryTreeNode(value)
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return self.right
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def test_full_tree(self):
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tree = Test.BinaryTreeNode(5)
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left = tree.insert_left(8)
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right = tree.insert_right(6)
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left.insert_left(1)
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left.insert_right(2)
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right.insert_left(3)
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right.insert_right(4)
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result = is_balanced(tree)
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self.assertTrue(result)
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def test_both_leaves_at_the_same_depth(self):
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tree = Test.BinaryTreeNode(3)
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left = tree.insert_left(4)
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right = tree.insert_right(2)
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left.insert_left(1)
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right.insert_right(9)
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result = is_balanced(tree)
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self.assertTrue(result)
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def test_leaf_heights_differ_by_one(self):
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tree = Test.BinaryTreeNode(6)
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left = tree.insert_left(1)
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right = tree.insert_right(0)
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right.insert_right(7)
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result = is_balanced(tree)
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self.assertTrue(result)
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def test_leaf_heights_differ_by_two(self):
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tree = Test.BinaryTreeNode(6)
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left = tree.insert_left(1)
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right = tree.insert_right(0)
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right_right = right.insert_right(7)
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right_right.insert_right(8)
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result = is_balanced(tree)
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self.assertFalse(result)
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def test_three_leaves_total(self):
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tree = Test.BinaryTreeNode(1)
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left = tree.insert_left(5)
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right = tree.insert_right(9)
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right.insert_left(8)
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right.insert_right(5)
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result = is_balanced(tree)
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self.assertTrue(result)
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def test_both_subtrees_superbalanced(self):
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tree = Test.BinaryTreeNode(1)
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left = tree.insert_left(5)
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right = tree.insert_right(9)
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right_left = right.insert_left(8)
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right.insert_right(5)
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right_left.insert_left(7)
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result = is_balanced(tree)
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self.assertFalse(result)
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def test_both_subtrees_superbalanced_two(self):
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tree = Test.BinaryTreeNode(1)
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left = tree.insert_left(2)
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right = tree.insert_right(4)
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left.insert_left(3)
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left_right = left.insert_right(7)
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left_right.insert_right(8)
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right_right = right.insert_right(5)
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right_right_right = right_right.insert_right(6)
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right_right_right.insert_right(9)
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result = is_balanced(tree)
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self.assertFalse(result)
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def test_only_one_node(self):
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tree = Test.BinaryTreeNode(1)
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result = is_balanced(tree)
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self.assertTrue(result)
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def test_linked_list_tree(self):
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tree = Test.BinaryTreeNode(1)
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right = tree.insert_right(2)
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right_right = right.insert_right(3)
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right_right.insert_right(4)
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result = is_balanced(tree)
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self.assertTrue(result)
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unittest.main(verbosity=2)
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