我是完全新的蟒蛇，我目前正在通过关于河内和递归塔教程。我想，我递归，直到他们给这个例子中明白了：

i'm completely new to python and I am currently going over a tutorial about the towers of Hanoi and recursion. I thought that I understood recursion until they gave this example:

def moveTower(height,fromPole, toPole, withPole):
    if height >= 1:
        moveTower(height-1,fromPole,withPole,toPole)
        moveDisk(fromPole,toPole)
        moveTower(height-1,withPole,toPole,fromPole)
    #print(withPole)

def moveDisk(fp,tp):
    print("moving disk from",fp,"to",tp)


moveTower(3,"A","B","C")

打印出正确的移动解决河内问题的塔与3盘： 从A盘移动到B 移动硬盘从A至C 移动磁盘从B到C 从A盘移动到B 移动硬盘从C到A 从C盘移动到B 移动硬盘从A到B

which prints the correct moves for solving the towers of hanoi problem with 3 discs: moving disk from A to B moving disk from A to C moving disk from B to C moving disk from A to B moving disk from C to A moving disk from C to B moving disk from A to B

我的问题是，它是如何做到这一点！？可能有人走过去的code中的线，让我明白它是如何打印正确的举动？我主要困惑着如何FP和TP的价值可以从改变到B到C.很抱歉，如果这是一个广泛的问题，一点！任何帮助将大大AP preciated！

my question is, how does it do so!? could someone go over the lines of code so that I understand how it prints the correct moves? i'm mainly confused with how the value of fp and tp can change from A to B to C. Sorry if this is bit of a broad question! Any help would be greatly appreciated!

推荐答案

在这个简单的情况下，你可以想像使用适当的打印 S，这样会发生什么：

In this simple case you can just visualize what happens by using appropriate prints, like this:

def moveTower(height,fromPole, toPole, withPole):
    if height >= 1:
        print( "    "*(3-height), "moveTower:", height, fromPole, toPole )
        moveTower(height-1,fromPole,withPole,toPole)
        moveDisk(fromPole,toPole,height)
        moveTower(height-1,withPole,toPole,fromPole)
    #print(withPole)

def moveDisk(fp,tp,height):
    print("    "*(4-height), "moving disk", "~"*(height), "from",fp,"to",tp)


moveTower(3,"A","B","C")

的输出是：

moveTower: 3 A B
     moveTower: 2 A C
         moveTower: 1 A B
             moving disk ~ from A to B
         moving disk ~~ from A to C
         moveTower: 1 B C
             moving disk ~ from B to C
     moving disk ~~~ from A to B
     moveTower: 2 C B
         moveTower: 1 C A
             moving disk ~ from C to A
         moving disk ~~ from C to B
         moveTower: 1 A B
             moving disk ~ from A to B