Created
April 22, 2015 04:06
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アルゴリズムクイックリファレンス:中央値ソート
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def sort(target): | |
median_sort(target, 0, len(target) - 1) | |
return target | |
def median_sort(target, left, right): | |
if left < right: | |
# find median | |
mid_point = (left + right) / 2 | |
min_value = target[left] | |
max_value = target[left] | |
index = left | |
while index <= right: | |
min_value = min(min_value, target[index]) | |
max_value = max(max_value, target[index]) | |
index += 1 | |
median_value = (max_value + min_value) / 2 | |
median_point = target.index(median_value) | |
# swap median to mid_point | |
swap(target, mid_point, median_point) | |
# partition left to right | |
left_point = left | |
while left_point <= mid_point - 1: | |
if target[left_point] > median_value: | |
right_point = mid_point + 1 | |
while right_point <= right: | |
if target[left_point] > target[right_point] and target[right_point] < median_value: | |
swap(target, target.index(target[left_point]), target.index(target[right_point])) | |
break | |
right_point += 1 | |
left_point += 1 | |
# swap left part | |
median_sort(target, left, mid_point - 1) | |
# swap right part | |
median_sort(target, mid_point + 1, right) | |
def swap(target, a, b): | |
target[b], target[a] = target[a], target[b] | |
return target |
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