52 lines
1.4 KiB
Python
52 lines
1.4 KiB
Python
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"""
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归并排序：类似快排，通过不断将列表折半来进行排序。
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如果集合为空或只有一个项，则按基本情况排序。
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如果有多项，则分割集合，并递归调用两个区间的归并排序。
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一旦对这两个区间排序完成，就执行合并操作。
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"""
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def merge_sort(nums: list[int], left: int, right: int, ):
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if left >= right:
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return
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mid = (left + right) >> 1
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merge_sort(nums, left, mid)
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merge_sort(nums, mid + 1, right)
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merge(nums, left, mid, right)
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def merge(nums: list[int], left: int, mid: int, right: int):
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# 临时数组存放合并后的结果
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temp = [0] * (right - left + 1)
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# 初始化左、右字序列的起始索引，左从left开始，右从mid开始
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i, j, k = left, mid + 1, 0
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# 左边第一个肯定是左边最小的，右边第一个肯定是右边最小的
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while i <= mid and j <= right:
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if nums[i] <= nums[j]:
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temp[k] = nums[i]
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i += 1
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else:
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temp[k] = nums[j]
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j += 1
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k += 1
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# 比较终结时，可能由于对折不均，仍有一边右数没有添加到临时列表中
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while i <= mid:
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temp[k] = nums[k]
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i += 1
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k += 1
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while j <= right:
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temp[k] = nums[j]
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j += 1
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k += 1
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# 将临时数组中的元素复制回原数组对应的位置
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for k in range(len(temp)):
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nums[left + k] = temp[k]
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