36 lines
771 B
Python
36 lines
771 B
Python
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import re
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start = 134792
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end = 675810
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def satisfies(x):
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x = str(x)
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result = False
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double, not_decreasing = False, False
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# double and *only* double exists
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for i in range(len(x) - 1):
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# double and left-of-a is BOL or !x
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# and right-of-b is EOL or !x
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a, b = x[i], x[i + 1]
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bol = i - 1 < 0
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eol = i + 2 >= len(x)
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if a == b and (bol or x[i - 1] != a) and (eol or x[i + 2] != a):
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double = True
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break
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# not_decreasing
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prev = int(x[0])
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for a in x[1:]:
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a = int(a)
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if prev > a:
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return False
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prev = a
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not_decreasing = True
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return double and not_decreasing
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print(len([x for x in range(start, end + 1) if satisfies(x)]))
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