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; }