uva 10263

求所有線段中，最靠近m點且再線段上面的座標是多少

模板題，參考git資料

//
//        GGGGGGGGGGGGG        CCCCCCCCCCCCC               AAA
//     GGG::::::::::::G     CCC::::::::::::C              A:::A
//   GG:::::::::::::::G   CC:::::::::::::::C             A:::::A
//  G:::::GGGGGGGG::::G  C:::::CCCCCCCC::::C            A:::::::A
// G:::::G       GGGGGG C:::::C       CCCCCC           A:::::::::A
//G:::::G              C:::::C                        A:::::A:::::A
//G:::::G              C:::::C                       A:::::A A:::::A
//G:::::G    GGGGGGGGGGC:::::C                      A:::::A   A:::::A
//G:::::G    G::::::::GC:::::C                     A:::::A     A:::::A
//G:::::G    GGGGG::::GC:::::C                    A:::::AAAAAAAAA:::::A
//G:::::G        G::::GC:::::C                   A:::::::::::::::::::::A
// G:::::G       G::::G C:::::C       CCCCCC    A:::::AAAAAAAAAAAAA:::::A
//  G:::::GGGGGGGG::::G  C:::::CCCCCCCC::::C   A:::::A             A:::::A
//   GG:::::::::::::::G   CC:::::::::::::::C  A:::::A               A:::::A
//     GGG::::::GGG:::G     CCC::::::::::::C A:::::A                 A:::::A
//        GGGGGG   GGGG        CCCCCCCCCCCCCAAAAAAA                   AAAAAAA
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
#include <ctime>
using namespace std;
#ifdef DEBUG
#define VAR(a,b) decltype(b) a=(b)
#define debug(...) printf("DEBUG: "),printf(__VA_ARGS__)
#define gettime() end_time=clock();printf("now running time is %.7f\n",(float)(end_time - start_time)/CLOCKS_PER_SEC);
#else
#define VAR(a,b) __typeof(b) a=(b)
#define debug(...)
#define gettime()
#endif
typedef unsigned int uint;
typedef long long int Int;
typedef unsigned long long int UInt;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\n")
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()
#define De(x)printf(#x"%d\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\
    printf("%d ",dp[htx][hty]);}Pln();}
#define M 30005
#define PII pair<int,int>
#define PB push_back
#define oo INT_MAX
#define Set_oo 0x3f
#define FOR(a,b) for(VAR(a,(b).begin());a!=(b).end();++a)
#define eps 1e-6
#define X first
#define Y second
clock_t start_time=clock(), end_time;
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
    int tmp=min(x,y);
    return min(tmp,z);
}
int max3(int x,int y,int z){
    int tmp=max(x,y);
    return max(tmp,z);
}
double mx,my;
struct point{
    double x,y;
    point(){
        x=y=oo;
    }
    point(double x,double y):x(x),y(y){};
};
struct vec{
    double x,y;
    vec(double x,double y):x(x),y(y){};
    double operator%(vec d){
        return (x*d.x+y*d.y);
    }
    double operator*(vec d){
        return (x*d.y-y*d.x);
    }
    double length(){
        return sqrt(x*x+y*y);
    }
    double NormalSqr(){
        return x*x+y*y;
    }
};
vec toVector(point p1,point p2){
    return vec(p2.x-p1.x,p2.y-p1.y);
}
vec scaleVector(vec v,double s){
    return vec(v.x*s,v.y*s);
}
point translate(point p,vec v){
    return point(p.x+v.x,p.y+v.y);
}
double dist(point a,point b){
    //return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
    return hypot(a.x-b.x,a.y-b.y);
}
double distToLine(point o,point a,point b,point &LineP){
    vec ao=toVector(a,o),ab=toVector(a,b);
    double u=(ao%ab)/ab.NormalSqr();
//    debug("%lf\n",u);
    LineP=translate(a,scaleVector(ab,u));
    return dist(LineP,o);
}
double distToLineSegment(point o,point a,point b,point &LineP){
    vec ao=toVector(a,o),ab=toVector(a,b);
    double u=(ao%ab)/ab.NormalSqr();
    if(u<0.0){
        LineP=point(a.x,a.y);
        return dist(o,a);
    }
    if(u>1.0){
        LineP=point(b.x,b.y);
        return dist(o,b);
    }
    return distToLine(o,a,b,LineP);
}
int n;

int main() {
    ios_base::sync_with_stdio(0);
    point rail[105],m;
    while(~scanf("%lf%lf",&mx,&my)){
        m=point(mx,my);
        scanf("%d",&n);
        for(int i=0;i<=n;i++){
            double x,y;
            scanf("%lf%lf",&x,&y);
            rail[i]=point(x,y);
        }
        double minn=oo;
        point ans,pt;
        for(int i=0;i<n;i++){
            double t=distToLineSegment(m,rail[i],rail[i+1],pt);
//            debug("%lf\n",t);
            if(t<minn){
                minn=t;
                ans=pt;
            }
        }
        printf("%.4lf\n%.4lf\n",ans.x,ans.y);
    }

















}