HDU1395+快速幂 

 1 #include<stdio.h>
 2 int fast_pow( int a,int b,int mod ){
 3     int res = 1;
 4     while( b>=1 ){
 5         if( b%2==1 ){
 6             res = res*a%mod;
 7         }
 8         a = a*a%mod;
 9         b/=2;
10     }
11     return res;
12 }
13 int main(){
14     int n;
15     while( ~scanf("%d",&n) ){
16         if( n==1||n%2==0 ){
17             printf("2^? mod %d = 1\n",n);
18             continue;
19         }
20         int ans = 2;
21         while( 1 ){
22             if( fast_pow( 2,ans,n )==1 ) 
23                 break;
24             ans++;
25         }
26         printf("2^%d mod %d = 1\n",ans,n);
27     }
28     return 0;
29 }
View Code

 

posted @ 2013-07-07 23:17  xxx0624  阅读(220)  评论(0)  编辑  收藏  举报