题解 | 【模板】点线最近距离

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

typedef long long ll;
const double EPS=1e-8;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout<<fixed<<setprecision(10);
    int q;
    cin>>q;
    while(q--){
        int op;
        cin>>op;
        ll x1,x2,x3,y1,y2,y3;
        cin>>x1>>y1>>x2>>y2>>x3>>y3;
        ll dx=x2-x1;
        ll dy=y2-y1;
        ll cx=x3-x1;
        ll cy=y3-y1;
        ll dot=cx*dx+cy*dy;
        ll lensq=dx*dx+dy*dy;
        double t=(double)dot/lensq;
        if(op==1||op==2){
            double px=x1+t*dx;
            double py=y1+t*dy;
            if(op==1){
                cout<<px<<" "<<py<<endl;
            }
            else {
                ll cross=abs(dx*cy-dy*cx);
                double dis=(double)cross/sqrt(lensq);
                cout<<dis<<endl;
            }
        }
        else{
            if(t<0)t=0;
            if(t>1)t=1;
            double px=x1+t*dx;
            double py=y1+t*dy;
            if(op==3){
                cout<<px<<" "<<py<<endl;
            }
            else{
                double dcx=px-x3;
                double dcy=py-y3;
                double dis=sqrt(dcx*dcx+dcy*dcy);
                cout<<dis<<endl;
            }
        }
    }
    return 0;
}