题解 | 绕距

#include <cmath>
#include <iomanip>
#include <iostream>
using namespace std;

int main() {
    int x1, x2, y1, y2;
    cin >> x1 >> y1;
    cin >> x2 >> y2;
    double dE = (double) sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
    double dM = (double) abs(x1 - x2) + abs(y1 - y2);
    double res = abs(dM - dE);

    cout << fixed << setprecision(9) << res << endl;
}
// 64 位输出请用 printf("%lld")

sqrt（）：求开根号

abs（）：求绝对值