实例：汉诺塔问题

n个圆盘3个柱子abc 一次动一个盘子

把上面n-1个盘看成一个整体，下面1个盘看成一个整体

• n-1盘经过c移动到b
• 第n盘到c
• n-1盘经过a到c

1 3步就是小一规模的汉诺塔
移动次数递推式 h(x)=2h(x-1)+1

def hanoi(n, a, b, c):
    if n > 0:
        hanoi(n - 1, a, c, b)
        print("moving from %s to %s" % (a, c))
        hanoi(n - 1, b, a, c)


hanoi(3, 'A', 'B', 'C')

# moving from A to C
# moving from A to B
# moving from C to B
# moving from A to C
# moving from B to A
# moving from B to C
# moving from A to C