杭电2001

注意看清输入是X1，Y1，X2，Y2，就因为把输入顺序看错了，错了好几次

#include<iostream>#include<iomanip>#include<cmath>using namespace std;int main(){    double x1,x2,y1,y2;    while(cin>>x1>>y1>>x2>>y2)    {         cout<<setiosflags(ios::fixed)<<setprecision(2)<<sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))<<endl;     }    return 0;}