题解 | 绕距

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

int main() {
  
    int x1, y1, x2, y2;
 
    cin >> x1 >> y1;
    cin >> x2 >> y2;

    double dx = x1 - x2;
    double dy = y1 - y2;

 
    double dM = fabs(dx) + fabs(dy);
 
    double dE = sqrt(pow(dx, 2) + pow(dy, 2));
    
    double delta = fabs(dM - dE);

    cout << fixed << setprecision(12) << delta << endl;

    return 0;
}