Python 生成全排列

def print_res(a):
    print(a)


def swap(a, i, j):
    temp = a[i]
    a[i] = a[j]
    a[j] = temp


def dfs(a, depth):
    if depth == len(a):
        print_res(a)
    for i in range(depth, len(a)):
        swap(a, i, depth)
        dfs(a, depth + 1)
        swap(a, depth, i)

a = [1, 3, 5, 7]
dfs(a, 0)