题解 | 绕距

#include<bits/stdc++.h> 
#include <cmath>
using namespace std;
int main(){
    int a,b,c,d;
    double E,F,G;
    cin>>a>>b>>c>>d;
    E=sqrt((a-c)*(a-c)+(b-d)*(b-d));
    F=(fabs(a-c))+(fabs(b-d));
    G=fabs(F-E);
    cout<<fixed<<setprecision(6)<<G;
    return 0;
}