c语言判断某个点是否在凸四边形内部,边界范围用

#include <stdio.h>
#include <stdbool.h>
#include <math.h>typedef struct {double x, y;
} Pointxy;// 计算向量叉积 (p2-p1) × (p3-p1)
static double crossProduct(Pointxy p1, Pointxy p2, Pointxy p3) {return (p2.x - p1.x) * (p3.y - p1.y) - (p2.y - p1.y) * (p3.x - p1.x);
}
// 判断点是否在线段上（考虑浮点数精度）
static bool isPointOnSegment(Pointxy p1, Pointxy p2, Pointxy p) {// 计算叉积，如果为0则点在线段所在直线上double cross = crossProduct(p1, p2, p);if (fabs(cross) > 1e-10) {return false;}// 检查点是否在两个端点之间double min_x = fmin(p1.x, p2.x);double max_x = fmax(p1.x, p2.x);double min_y = fmin(p1.y, p2.y);double max_y = fmax(p1.y, p2.y);return (p.x >= min_x - 1e-10 && p.x <= max_x + 1e-10 &&p.y >= min_y - 1e-10 && p.y <= max_y + 1e-10);
}
// 判断点是否在凸四边形内部
static bool isPointInConvexQuad(Pointxy quad[4], Pointxy p) {// // 检查点是否在四边形的边界上// for (int i = 0; i < 4; i++) {//     if (isPointOnSegment(quad[i], quad[(i + 1) % 4], p)) {//         return true;//     }// }// 检查点是否在所有边的同一侧（对于凸四边形）double d1 = crossProduct(quad[0], quad[1], p);double d2 = crossProduct(quad[1], quad[2], p);double d3 = crossProduct(quad[2], quad[3], p);double d4 = crossProduct(quad[3], quad[0], p);// // 对于凸四边形，所有叉积应该同号（都在内部或都在外部）// // 我们检查是否都在内部（>0）或都在外部（<0）bool has_neg = (d1 < 0) || (d2 < 0) || (d3 < 0) || (d4 < 0);bool has_pos = (d1 > 0) || (d2 > 0) || (d3 > 0) || (d4 > 0);return !(has_neg && has_pos);
}// 判断矩形是否在凸四边形内部
static bool isBoxInConvexQuad(Pointxy quad[4], Pointxy boxMin, Pointxy boxMax) {// 矩形的四个顶点Pointxy vertices[4] = {{boxMin.x, boxMin.y},{boxMin.x, boxMax.y},{boxMax.x, boxMin.y},{boxMax.x, boxMax.y}};//任何一个在里面,就满足for (int i = 0; i < 4; i++) {if (isPointInConvexQuad(quad, vertices[i])) {return true;}}return false;// // 检查矩形的每个顶点是否都在四边形内部// for (int i = 0; i < 4; i++) {//     if (!isPointInConvexQuad(quad, vertices[i])) {//         return false;//     }// }// return true;
}// 定义一个凸四边形（按顺时针或逆时针顺序）
Pointxy quad[4] = {{10, 10},{20, 10},{25, 20},{ 5, 20}
};
void test_point(Pointxy testPoint){// Pointxy testPoint = {5, 2};printf("点 x:%lf,y:%lf  ",testPoint.x,testPoint.y);if (isPointInConvexQuad(quad, testPoint)) {printf("点在四边形内部\n");} else {printf("点不在四边形内部\n");}
}
void test_box(Pointxy boxMin,Pointxy boxMax){// Pointxy boxMin = {1, 1};// Pointxy boxMax = {5, 5};printf("box x:%lf,y:%lf w:%lf,h:%lf  ",boxMin.x,boxMin.y,boxMax.x-boxMin.x,boxMax.y-boxMin.y);if (isBoxInConvexQuad(quad, boxMin, boxMax)) {printf("矩形在四边形内部\n");} else {printf("矩形不在四边形内部\n");}
}// 编译运行  g++ 00_test_box.cpp -o 00_test_box && ./00_test_box
int main() {// 测试点printf("\n\ntest 点 外面\n");//外面test_point({0,0});test_point({15,5});test_point({5,15});test_point({15,25});test_point({25,15});//里面printf("\n\ntest 点 里面\n");test_point({15,15});test_point({11,11});test_point({10,10});// 测试矩形printf("\n\ntest 矩形\n");test_box({1,1},{5,5});//外test_box({1,1},{15,15});//里return 0;
}