用c++写出一个点是否在多边形的判断方法
时间: 2023-12-22 08:03:01 浏览: 29
以下是一个简单的点是否在多边形的判断方法:
```c
#include <stdio.h>
#define MAX_VERTICES 100
typedef struct {
double x, y;
} Point;
typedef struct {
int n;
Point p[MAX_VERTICES];
} Polygon;
double cross_product(Point a, Point b, Point c) {
return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
}
int is_inside_polygon(Point q, Polygon poly) {
int i, j, c = 0;
for (i = 0, j = poly.n-1; i < poly.n; j = i++) {
if (((poly.p[i].y > q.y) != (poly.p[j].y > q.y)) &&
(q.x < (poly.p[j].x - poly.p[i].x) * (q.y - poly.p[i].y) / (poly.p[j].y - poly.p[i].y) + poly.p[i].x))
c = !c;
}
return c;
}
int main() {
Polygon poly = {4, {{0,0}, {0,1}, {1,1}, {1,0}}};
Point p = {0.5, 0.5};
if (is_inside_polygon(p, poly))
printf("The point is inside the polygon.\n");
else
printf("The point is outside the polygon.\n");
return 0;
}
```
该方法使用射线法,将从点向右发出的射线与多边形的每条边进行交点计算,根据交点的奇偶性来判断点是否在多边形内部。如果交点的数量为奇数,则点在多边形内部,否则在外部。
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