019f8fd211
git-subtree-dir: users/wpcarro git-subtree-mainline:464bbcb15cgit-subtree-split:24f5a642afChange-Id: I6105b3762b79126b3488359c95978cadb3efa789
62 lines
1.5 KiB
Python
62 lines
1.5 KiB
Python
from collections import deque
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def move_zeroes_to_end_quadratic(xs):
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"""
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This solution is suboptimal. It runs in quadratic time, and it uses constant
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space.
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"""
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i = 0
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while i < len(xs) - 1:
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if xs[i] == 0:
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j = i + 1
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while j < len(xs) and xs[j] == 0:
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j += 1
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if j >= len(xs):
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break
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xs[i], xs[j] = xs[j], xs[i]
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i += 1
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def move_zeroes_to_end_linear(xs):
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"""
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This solution is clever. It runs in linear time proportionate to the number
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of elements in `xs`, and has linear space proportionate to the number of
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consecutive zeroes in `xs`.
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"""
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q = deque()
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for i in range(len(xs)):
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if xs[i] == 0:
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q.append(i)
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else:
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if q:
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j = q.popleft()
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xs[i], xs[j] = xs[j], xs[i]
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q.append(i)
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def move_zeroes_to_end_linear_constant_space(xs):
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"""
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This is the optimal solution. It runs in linear time and uses constant
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space.
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"""
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i = 0
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for j in range(len(xs)):
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if xs[j] != 0:
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xs[i], xs[j] = xs[j], xs[i]
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i += 1
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################################################################################
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# Tests
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################################################################################
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xss = [
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[1, 2, 0, 3, 4, 0, 0, 5, 0],
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[0, 1, 2, 0, 3, 4],
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[0, 0],
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]
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f = move_zeroes_to_end_linear_constant_space
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for xs in xss:
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print(xs)
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f(xs)
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print(xs)
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