ACM PKU 2244 Eeny Meeny Moo 约瑟夫问题
http://acm.pku.edu.cn/JudgeOnline/problem?id=2244
在没有明白约瑟夫问题之前,只能用模拟来做.
约瑟夫问题是这样的:
假设n个人,编号为1到n,排成一个圈,顺时针从1开始数字m,数到m的人杀了,剩下的人继续游戏.活到最后的一个人是胜利者.一般来说需要编程求解最后一个人的编号.
思路是这样的:
假设当前剩下i个人(i<=n),显然这一轮m要挂(因为总是从1开始数).经过这一轮,剩下的人是:1 2 3 ... m- 1 m + 1
... i, 我们将从m+1开始的数映射成1, 则m+2对应2, n对应i - m, 1对应成i - m + 1 m - 1对应i -
1,那么现在的问题变成了已知i - 1个人进行循环报数m,求出去的人的序号。假设已经求出了i-
1个人循环报数下最后一个出去的人的序号X0,那么它在n个人中的序号X1=(X0+ m - 1) % n + 1, 最初的X0=1
,反复迭代X0和X1可以求出.
简单约瑟夫问题的解法:
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参考代码如下:
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