太简单了

本质：勾股定理

#include<bits/stdc++.h>
using namespace std;
double solve_distant(int x, int y, int x1, int y1){ //改成int不会保留两位小数 
    int a = x1 - x; //求出a边
    int b = y1 - y;//求出b边
    return sqrt(a * a + b * b);//求出c边
}
int main(){
    int x, y, x1, y1;
    cin >> x >> y >> x1 >> y1;
    cout << fixed << setprecision(2) << solve_distant(x, y, x1, y1);
}