题解 | 点到直线距离|向量投影+勾股定理

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

struct point{
    double x,y;
    point(double A,double B){
        x=A,y=B;
    }
    point() = default;
};

struct line{
    point point_A,point_B;
    line(point A,point B){
        point_A = A,point_B = B;
    }
    line() = default;
};

double getDistance(point P, line L){
    // TODO: 计算点P到直线L的距离
    double vecLine[4],vecPoint[4];
    vecLine[1]=L.point_A.x-L.point_B.x;
    vecLine[2]=L.point_A.y-L.point_B.y;
    vecPoint[1]=L.point_A.x-P.x;vecPoint[2]=L.point_A.y-P.y;
    double dotpro=vecLine[1]*vecPoint[1]+vecLine[2]*vecPoint[2];
    double molLine=sqrt(vecLine[1]*vecLine[1]+vecLine[2]*vecLine[2]);
    double sqmolPoint=(vecPoint[1]*vecPoint[1]+vecPoint[2]*vecPoint[2]);
    return sqrt(sqmolPoint-((dotpro)/(molLine))*((dotpro)/(molLine)));
}















































































































int main(){
    int a, b, sx, sy, tx, ty;
    cin >> a >> b >> sx >> sy >> tx >> ty;
    point A(sx, sy), B(tx, ty), C(a, b);
    line L(A, B);
    printf("%.2lf", getDistance(C, L));
    return 0;
}