递归，汉诺塔游戏

def hanoi(n,a,b,c):
    if n==1:
        print(n,a+'->'+c)
    else:
         hanoi(n-1,a,c,b)
         print(n,a+'->'+c)
         hanoi(n-1,b,a,c)


hanoi(9,'A','B','C')

def hanoi(n,a,b,c):
    if n==1:
        print(n,a+'->'+c)
    else:
         hanoi(n-1,a,c,b)
         print(n,a+'->'+c)
         hanoi(n-1,b,a,c)


hanoi(7,'A','B','C')

hanoi(7)
    hanoi(6)
        hanoi(5)
            hanoi(4)
                hanoi(3)
                    hanoi(2) 参数递减
                        move(1,退出条件)