---

 #include <iostream>
#include <cstdlib>
#include <math.h>
#include <cstring>
#include <algorithm>  
#include <string.h> 
#include <iomanip>
using namespace std ; 

int gcd (int a ,int  b)
{
 if(a%b==0)
 {
  return b ;
 }else 
 {
  return gcd(b,a%b) ;
 }
}
int main(void)
{
  int x ;
  
  while(cin>> x && x!=0)
  {
  int arr[100000] ; 
     for(int i=1;i<=x;i++)
	 {
	 cin >> arr[i];
	 }
	 
	 int countp=0;
	 int countd=0;
	  for(int i=0 ;i<x;i++)
	  {
	    for(int j=i+1;j<x;j++)
		{
		 countp++ ; 
		 if(gcd(arr[i],arr[j])==1)
		  {
		  countd++ ;
		  }
		}
	  }
	  if(countd==0)
	  {
	    cout << "No estimate for this data set." << endl ;
	  }else 
	   {
	     double a = countp*6.0/ countd ;
		 double answer = sqrt(a) ;
		 answer = round(answer*1000000);
		 answer = answer/1000000;
		cout  <<  setprecision(7)  << answer  <<  endl;
	   }
  }
 return 0;
 }
第 1 測資點(100%):   WA(line:1) 答案不正確 您的答案為: 3.464102 正確答案為: 3.162278  

想問一下是哪邊不對= = 

 

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找到問題點了 第一個 for 起始錯誤 ....我靠