题解 | 绕距

#include <bits/stdc++.h>
using namespace std;

int main() 
{
    int x1,y1,x2,y2;
    cin>>x1>>y1>>x2>>y2;
    double dE=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
    double dM=abs(x1-x2)+abs(y1-y2);
    double derta=abs(dM-dE);
    cout<<fixed<<setprecision(18)<<derta;
    return 0;
}