全排列算法实现

def ascii_permutation(arr:list):
    length = len(arr)

    while(True):
        print(arr)

        for i in range(length-1,-1, -1):
            if arr[i-1] < arr[i]:
                x = i-1
                break

        if i == 0:
            return

        for j in range(length-1, x, -1):
            if arr[j] > arr[x]:
                y = j
                break


        arr[x], arr[y] = arr[y], arr[x]
        sub = arr[x+1:]
        sub.reverse()
        arr = arr[0:x+1] + sub

def recursive_permutation(arr:list, start:int, end:int):
    if start == end:
        print(arr)

    else:
        for i in range(start, end):
            arr[i], arr[start] = arr[start], arr[i]
            recursive_permutation(arr, start+1, end)
            arr[i], arr[start] = arr[start], arr[i]

#arr = [1,2,3,4]

#ascii_permutation(arr)
#print('****************')
#recursive_permutation(arr,0,len(arr))