循环-02. 计算圆周率(15)

 1 #include<iostream>
 2 #include<iomanip>
 3 using namespace std;
 4 int main(){
 5     double t,pai=1,son=1,mum=1;
 6     int i=1;
 7     cin>>t;
 8     while(son/mum>=t){
 9         son*=i;
10         mum*=2*i+1;
11         pai+=son/mum;
12         i++;
13     }
14     cout<<setiosflags(ios::fixed)<<setprecision(6)<<2*pai<<endl;
15     return 0;
16 }