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用python实现冒泡排序和选择排序(Python经典编程案例)

中英双语视频 83

前言:

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1.冒泡排序:

def bubble_sort(list):    for i in range(0, len(list)):        is_sorted = True        for j in range(0, len(list) - i - 1):            if list[j] > list[j + 1]:                list[j], list[j + 1] = list[j + 1], list[j]                is_sorted = False        if is_sorted:            returnlist1 = [97, 3, 6, 1, 8, 5, -20, 100, 50, 200, -32, 123]bubble_sort(list1)print(list1)

执行结果如下图:

2.选择排序:

def choose_sort(list):    list_len = len(list)    for i in range(0, list_len):        for j in range(i + 1, list_len):            if list[i] > list[j]:                list[i], list[j] = list[j], list[i]                list1 = [3, 6, 1, 8, 5, -20, 100, 50, 200]choose_sort(list1)print(list1)

执行结果如下图:

3.选择排序、冒泡排序、插入排序、快速排序:

# -*- encoding: utf-8 -*-import random# O(n^2)def selection_sort(lyst):    """选择排序"""    i = 0    while i < len(lyst) - 1:        min_index = i        j = i + 1        while j < len(lyst):            if lyst[j] < lyst[min_index]:                min_index = j            j += 1        if i != min_index:            lyst[i], lyst[min_index] = lyst[min_index], lyst[i]        i += 1# O(n^2)def bubble_sort(lyst):    """冒泡排序"""    # 外层循环len(lyst) - 1, j最大能取到倒数第二个值, j+1取到最后一个    for i in range(1, len(lyst)):        for j in range(0, len(lyst) - 1):            if lyst[j] > lyst[j + 1]:                lyst[j], lyst[j + 1] = lyst[j + 1], lyst[j]# O(n^2)def insertion_sort(lyst):    """插入排序"""    # i=1, 表示假定 lyst[0] 为有序数据, 下一个为无序数据    for i in range(1, len(lyst)):        item = lyst[i]        j = i - 1        while j >= 0:            # 如果待排数据小于lyst[j], 就往后覆盖赋值            if item < lyst[j]:                lyst[j + 1] = lyst[j]                j -= 1            # 因为lyst[j] 是当前有序数值中最大的数, 如果比它还大就直接跳出            else:                break        # j 多减了1        lyst[j + 1] = item# O(nlogn)# 两种快速排序代码def quick_sort(lyst, left, right):    """快速排序"""    middle = (left + right) // 2    # 基准点    pivot = lyst[middle]    if left < right:        # 边界        boundary = left        # 将基准点与最后一个点交换        lyst[middle], lyst[right] = lyst[right], lyst[middle]        # 遍历边界右边, 是否小于基准点        for index in range(left, right):            if lyst[index] < pivot:                lyst[boundary], lyst[index] = lyst[index], lyst[boundary]                boundary += 1        lyst[boundary], lyst[right] = lyst[right], lyst[boundary]        # 左右子列表        quick_sort(lyst, left, boundary - 1)        quick_sort(lyst, boundary + 1, right)def quick_sort2(lyst, left, right):    """快速排序的另一种实现"""    if left >= right:        return None    # 基准点    pivot = lyst[left]    i, j = left, right    while i < j:        # 右分区向左        while i < j and lyst[j] > pivot:            j -= 1        if i < j:  # 交换            lyst[i], lyst[j] = lyst[j], lyst[i]            i += 1        # 左分区向右        while i < j and lyst[i] < pivot:            i += 1        if i < j:  # 交换            lyst[i], lyst[j] = lyst[j], lyst[i]            j -= 1    lyst[i] = pivot    quick_sort2(lyst, left, i - 1)    quick_sort2(lyst, i + 1, right)def get_lyst(lyst):    lyst.clear()    for i in range(8):        lyst.append(random.randint(1, 8))def main():    lyst = []    print("selection_sort:")    get_lyst(lyst)    print(lyst)    selection_sort(lyst)    print(lyst)    print("\nbubble_sort:")    get_lyst(lyst)    print(lyst)    bubble_sort(lyst)    print(lyst)    print("\ninsertion_sort:")    get_lyst(lyst)    print(lyst)    insertion_sort(lyst)    print(lyst)    print("\nquick_sort:")    get_lyst(lyst)    print(lyst)    quick_sort(lyst, 0, len(lyst) - 1)    print(lyst)    print("\nquick_sort2:")    get_lyst(lyst)    print(lyst)    quick_sort(lyst, 0, len(lyst) - 1)    print(lyst)if __name__ == '__main__':    main()

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