• 八大排序算法的python实现


    # -*- coding: utf-8 -*-
     
    # 冒泡排序
    def bubble_sort(nums):
        i = 1
        exchanged = True
        while i < len(nums) and exchanged:
            exchanged = False
            for j in range(len(nums) - i):
                if nums[j] > nums[j + 1]:
                    nums[j], nums[j + 1] = nums[j + 1], nums[j]
                    exchanged = True
            i += 1
        return nums
     
     
    # 快速排序
    def quick_sort(nums, left=0, right=None):
        if right == None:
            right = len(nums) - 1
        if left >= right:
            return nums
        low = left
        high = right
        key = nums[left]
        while left < right:
            while left < right and nums[right] >= key:
                right -= 1
            nums[left], nums[right] = nums[right], nums[left]
            while left < right and nums[left] <= key:
                left += 1
            nums[left], nums[right] = nums[right], nums[left]
        quick_sort(nums, low, left - 1)  # 递归
        quick_sort(nums, right + 1, high)  # left == right
        return nums
     
     
    # 插入排序
    def insert_sort(nuns):
        for i in range(1, len(nums)):
            key = nums[i]
            i -= 1
            while i >= 0 and nums[i] > key:
                nums[i + 1] = nums[i]
                i -= 1
            nums[i + 1] = key
        return nums
     
     
    # 希尔排序
    def shell_sort(nums):
        gap = len(nums) // 2  # 初始增量,//整除
        while gap > 0:
            # 缩小增量,直至增量为1
            for i in range(0, gap):
                # 分组
                j = i + gap
                while j < len(nums):
                    # 组内插入排序
                    key = nums[j]
                    k = j - gap
                    while k >= 0 and nums[k] > key:
                        nums[k + gap] = nums[k]
                        k -= gap
                    nums[k + gap] = key
                    j += gap
            gap //= 2
        return nums
     
     
    # 选择排序
    def select_sort(nums):
        for i in range(len(nums)):
            minimum = i
            for j in range(i + 1, len(nums)):
                if nums[j] < nums[minimum]:
                    minimum = j
            nums[i], nums[minimum] = nums[minimum], nums[i]
        return nums
     
     
    # 堆排序
    def max_heapify(nums, i, size):
        # 最大堆调整
        # 注意数组的size比数组的最大索引大1
        lchild = 2 * i + 1
        rchild = 2 * i + 2
        maximum = i
        if i < size // 2:
            if nums[lchild] > nums[maximum]:
                maximum = lchild
            if rchild < size:
                # 肯定有左子节点,未必有右子节点
                if nums[rchild] > nums[maximum]:
                    maximum = rchild
            if maximum != i:
                nums[i], nums[maximum] = nums[maximum], nums[i]
                max_heapify(nums, maximum, size)  # 递归
    def build_max_heap(nums, size):
        # 创建最大堆
        for i in range(size // 2 - 1, -1, -1):
            max_heapify(nums, i, size)
    def heap_sort(nums):
        size = len(nums)
        build_max_heap(nums, size)
        for i in range(1, size):
            nums[0], nums[size - i] = nums[size - i], nums[0]
            max_heapify(nums, 0, size - i)
        return nums
     
     
    # 归并排序
    def merge_sort(nums):
        length = len(nums)
        if length <= 1:
            return nums
        list1 = merge_sort(nums[: length // 2])
        list2 = merge_sort(nums[length // 2:])  # 递归
        i = 0
        j = 0
        k = 0
        while i < len(list1) and j < len(list2):
            if list1[i] < list2[j]:
                nums[k] = list1[i]
                i += 1
                k += 1
            else:
                nums[k] = list2[j]
                j += 1
                k += 1
            nums = nums[: k] + list1[i:]
            nums = nums[: k] + list2[j:]  # 其中一个为空列表
        return nums
     
     
    # 基数排序
    def radix_sort(nums):
        maximum = nums[0]
        for num in nums:
            # 找到最大值
            if num > maximum:
                maximum = num
        k = 1
        while maximum // (10 ** k) > 0:
            # 判定最大值是几位数
            k += 1
        for i in range(k):
            buckets = [[] for x in range(10)]
            for num in nums: 
                buckets[(num // (10 ** i)) % 10].append(num)
            nums = []
            for b in buckets:
                nums += b
        return nums
     
     
    # 测试
    nums0 = list(range(200))
    nums = list(range(200))
    random.shuffle(nums)
    print(bubble_sort(nums) == nums0)
    print(quick_sort(nums) == nums0)
    print(insert_sort(nums) == nums0)
    print(shell_sort(nums) == nums0)
    print(select_sort(nums) == nums0)
    print(heap_sort(nums) == nums0)
    print(merge_sort(nums) == nums0)
    print(radix_sort(nums) == nums0)
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  • 原文地址:https://www.cnblogs.com/brady-wang/p/9761868.html
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