hrbustOJ 受到攻击(判断点是否在凸多边形内包括边界)

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/*

*  题目要求：判断点是否在凸多边形内 

*  方法：利用叉乘判断拐向来求解  

*  auther:Try86 

*/

#include <cstdio>

#include <cstdlib>

#include <iostream>



using namespace std;



const int N = 100;



struct point {

    double x;

    double y;

}p[N], doTa;





double crossProd(point A, point B, point C){

    return (B.x-A.x)*(C.y-A.y) - (B.y-A.y)*(C.x-A.x);

}



bool isInside(int n) {

    bool yes = true;

    p[n] = p[0];

    for (int i=0; i<n; ++i) {

        if (crossProd(doTa, p[i], p[i+1]) < 0) {

            yes = false;

            break;

        }

    }

    return yes;

}



int main() {

    int n;

    while (scanf("%d%lf%lf", &n, &doTa.x, &doTa.y) != EOF) {

        for (int i=0; i<n; ++i) scanf ("%lf%lf",  &p[i].x, &p[i].y);

        bool yes = isInside(n);

        if (yes) printf ("Yes\n");

        else printf ("No\n");

    }

    return 0;

}