poj 1781 In Danger

约瑟夫问题

下面的博客写了常规的约瑟夫问题求解：http://blog.foreverzeus.com/?p=993

而这题比较蛋疼，o(n)竟然超时，最后找了规律，过了

#include<iostream>using namespace std;#include<cstring>#include<cmath>int mypow(int m,int n){int i,sum=1;for(i=1;i<=n;i++)sum*=m;return sum;}int mylog(int n){return (int)(log(n*1.0)/log(2.0));}int main(){int n;char ch[5];while(scanf("%s",ch)){if(!strcmp(ch,"00e0"))break;n=(ch[0]-'0')*mypow(10,ch[3]-'0'+1)+(ch[1]-'0')*mypow(10,ch[3]-'0');printf("%d/n",2*(n-mypow(2,mylog(n)))+1);}return 0;}