判断点是否在多边形内部C++代码实现

以下是判断点是否在多边形内部的C语言代码实现：

#include <stdio.h>
#include <stdbool.h>

typedef struct point {
    double x, y;
} Point;

int isLeft(Point a, Point b, Point c) {
    return ((b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x)) > 0;
}

bool isInsidePolygon(Point point, Point polygon[], int n) {
    int wn = 0;
    for (int i = 0; i < n; i++) {
        if (polygon[i].x <= point.x && polygon[i + 1].x > point.x && isLeft(polygon[i], polygon[i + 1], point))
            wn++;
        else if (polygon[i].x > point.x && polygon[i + 1].x <= point.x && isLeft(polygon[i + 1], polygon[i], point))
            wn--;
    }
    return wn != 0;
}

int main() {
    Point point = { 1.0, 1.0 };
    Point polygon[] = { {0.0, 0.0}, {0.0, 2.0}, {2.0, 2.0}, {2.0, 0.0}, {0.0, 0.0} };
    int n = sizeof(polygon) / sizeof(polygon[0]) - 1;
    bool result = isInsidePolygon(point, polygon, n);
    printf("Point (%lf, %lf) is%s inside the polygon\n", point.x, point.y, result ? "" : " not");
    return 0;
}

该实现使用了射线法。具体来说，对于多边形边界上的点，我们不认为它在多边形内部；对于多边形边界上的点，我们通过射线与多边形的交点个数来判断该点是否在多边形内部。如果交点个数为奇数，则该点在多边形内部，否则在多边形外部。