zoj1337

代码如下：

#include <stdio.h>#include<math.h>#include <string.h>int gcd(int a,int b);int main(){int N,i,j,count;int a[55];double PI;memset(a,0,55);while(scanf("%d",&N)&&N){count=0;for(i=0;i<N;i++){scanf("%d",&a[i]);}for(i=0;i<N;i++){for (j=i+1;j<N;j++){if (gcd(a[i],a[j])){count++;}}}if (count){PI=sqrt(3.0*N*(N-1)/count);printf("%.6lf\n",PI);}else{printf("No estimate for this data set.\n");}}return 0;}int gcd(int a,int b){int i;for(i=2;i<=a&&i<=b;i++){if (a%i==0&&b%i==0){return 0;}}return 1;}