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;
}