Python冒泡排序、选择排序、插入排序

1. 冒泡排序

def bubble_sort(alist):
    # 需操作 n-1 次
    for i in range(len(alist)-1, 0, -1):
        # 每次循环 i 次 
        for j in range(i):
            if alist[j] > alist[j+1]:
                alist[j], alist[j+1] = alist[j+1], alist[j]

if __name__ == '__main__':
    alist = [4, 1, 56, 34, 12, 18]
    bubble_sort(alist)
    print(alist)
   

2. 选择排序

def selection_sort(alist):
    n = len(alist)
    # 需要循环 n-1 次
    for i in range(n-1):
        # i位置默认最小值
        min_index = i

        # 从 i+1 位置循环到末尾找最小值
        for j in range(i+1, n):
            # 如果出现小于 i 位置值，则交换
            if alist[j] < alist[i]:
                min_index = j
                alist[i], alist[j] = alist[j], alist[i]

if __name__ == '__main__':
    alist = [12, 2, 34, 78, 6]
    selection_sort(alist)
    print(alist)

3. 插入排序

def insert_sort(alist):
    n = len(alist)

    # 从 1 位置开始，循环到末尾
    for i in range(1, n):
        # 从当前位置往前查找小于它的数
        for j in range(i, 0, -1):
            if alist[j] < alist[j-1]:
                alist[j-1],alist[j] = alist[j], alist[j-1]

if __name__ == '__main__':
    alist = [4, 8, 2, 1, 23, 15]
    insert_sort(alist)
    print(alist)