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feat: Add the section of heap sort. (#516)
* Add the section of heap sort. * Update heap_sort.cpp
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codes/python/chapter_sorting/heap_sort.py
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45
codes/python/chapter_sorting/heap_sort.py
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"""
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File: heap_sort.py
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Created Time: 2023-05-24
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Author: Krahets (krahets@163.com)
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"""
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def sift_down(nums: list[int], n: int, i: int):
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"""堆的长度为 n ,从节点 i 开始,从顶至底堆化"""
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while True:
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# 判断节点 i, l, r 中值最大的节点,记为 ma
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l = 2 * i + 1
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r = 2 * i + 2
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ma = i
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if l < n and nums[l] > nums[ma]:
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ma = l
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if r < n and nums[r] > nums[ma]:
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ma = r
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# 若节点 i 最大或索引 l, r 越界,则无需继续堆化,跳出
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if ma == i:
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break
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# 交换两节点
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nums[i], nums[ma] = nums[ma], nums[i]
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# 循环向下堆化
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i = ma
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def heap_sort(nums: list[int]):
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"""堆排序"""
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# 建堆操作:堆化除叶节点以外的其他所有节点
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for i in range(len(nums) // 2 - 1, -1, -1):
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sift_down(nums, len(nums), i)
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# 从堆中提取最大元素,循环 n-1 轮
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for i in range(len(nums) - 1, 0, -1):
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# 交换根节点与最右叶节点(即交换首元素与尾元素)
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nums[0], nums[i] = nums[i], nums[0]
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# 以根节点为起点,从顶至底进行堆化
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sift_down(nums, i, 0)
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"""Driver Code"""
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if __name__ == "__main__":
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nums = [4, 1, 3, 1, 5, 2]
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heap_sort(nums)
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print("堆排序完成后 nums =", nums)
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