Intersection POJ - 1410

Intersection POJ - 1410

题目链接：https://vjudge.net/problem/POJ-1410

题目：

 

 

 题意：判断线段与矩形是否有公共区域。。。一开始我以为判断线段与矩形四条边是否相交就行。。。没想到还有线段在矩形内部也算相交。。。

// 
// Created by HJYL on 2020/1/13.
//
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<queue>
#include<cmath>
#define eps 1e-8
#define Inf 0x7fffffff
//#include<bits/stdc++.h>
using namespace std;
const int maxn=1e5+100;
struct Point{
    double x,y;
};
double min(double a, double b) { return a < b ? a : b; }

double max(double a, double b) { return a > b ? a : b; }

bool IsSegmentIntersect(Point a, Point b, Point c, Point d)
{
    if( min(a.x, b.x) > max(c.x, d.x) ||
        min(a.y, b.y) > max(c.y, d.y) ||
        min(c.x, d.x) > max(a.x, b.x) ||
        min(c.y, d.y) > max(a.y, b.y) )
        return 0;

    double h, i, j, k;

    h = (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
    i = (b.x - a.x) * (d.y - a.y) - (b.y - a.y) * (d.x - a.x);
    j = (d.x - c.x) * (a.y - c.y) - (d.y - c.y) * (a.x - c.x);
    k = (d.x - c.x) * (b.y - c.y) - (d.y - c.y) * (b.x - c.x);

    return h * i <= eps && j * k <= eps;
}

int main()
{
    int T;
    while(~scanf("%d",&T)) {
        while (T--) {
            Point ju1, ju2, ju3, ju4, gun1, gun2;
            double gunx, guny, gun1x, gun1y, zsx, zsy, yxx, yxy;
            scanf("%lf%lf%lf%lf%lf%lf%lf%lf", &gunx, &guny, &gun1x, &gun1y, &zsx, &zsy, &yxx, &yxy);
            ju1.x = zsx;
            ju1.y = zsy;
            ju2.x = zsx;
            ju2.y = yxy;
            ju3.x = yxx;
            ju3.y = zsy;
            ju4.x = yxx;
            ju4.y = yxy;
            gun1.x = gunx;
            gun1.y = guny;
            gun2.x = gun1x;
            gun2.y = gun1y;
            double a=min(gunx,gun1x);
            double a1=max(gunx,gun1x);
            double b=min(guny,gun1y);
            double b1=max(guny,gun1y);
            double c=min(zsx,yxx);
            double c1=max(zsx,yxx);
            double d=min(zsy,yxy);
            double d1=max(zsy,yxy);
            if (IsSegmentIntersect(gun1, gun2, ju1, ju2) ||
                IsSegmentIntersect(gun1, gun2, ju1, ju3) ||
                IsSegmentIntersect(gun1, gun2, ju2, ju4) ||
                IsSegmentIntersect(gun1, gun2, ju3, ju4) ||
                    (a>=c&&a1<=c1&&b>=d&&b1<=d1)
                )
                printf("T\n");
            else
                printf("F\n");

        }
    }
    return 0;
}