Triangles FZU

题目大意：

给你两个三角形，判断他们的关系：包含，相交，相离

代码：

#include <iostream>#include <cmath>#include <cstdio>#define ABS_FLOAT_0  0.0001using namespace std;struct Point{    double x,y;};struct Triangle{    Point A,B,C;};//ab和ac两向量叉积double mult(Point a,Point b,Point c){    return (a.x-c.x)*(b.y-c.y)-(b.x-c.x)*(a.y-c.y);}//aa, bb为一条线段两端点 cc, dd为另一条线段的两端点 相交返回true, 不相交返回falsebool intersect(Point aa, Point bb, Point cc, Point dd){    if ( max(aa.x, bb.x)<min(cc.x, dd.x) )        return false;    if ( max(aa.y, bb.y)<min(cc.y, dd.y) )        return false;    if ( max(cc.x, dd.x)<min(aa.x, bb.x) )        return false;    if ( max(cc.y, dd.y)<min(aa.y, bb.y) )        return false;    if ( mult(cc, bb, aa)*mult(bb, dd, aa)<0 )        return false;    if ( mult(aa, dd, cc)*mult(dd, bb, cc)<0 )        return false;    return true;}//求三角形面积double Get_Triangle_Squar(Point A,Point B,Point C){    return fabs(mult(A,B,C))/2.0;}//判断点D是否在三角形ABC内bool IsInTriangle(const Point A, const Point B, const Point C, const Point D){    double SABC, SADB, SBDC, SADC;    SABC = Get_Triangle_Squar(A, B, C);    SADB = Get_Triangle_Squar(A, D, B);    SBDC = Get_Triangle_Squar(B, D, C);    SADC = Get_Triangle_Squar(A, D, C);    double SumSuqar = SADB + SBDC + SADC;    if ((-ABS_FLOAT_0 < (SABC - SumSuqar)) && ((SABC - SumSuqar) < ABS_FLOAT_0))        return true;    else        return false;}int main(){    int T;    scanf("%d",&T);    while(T--)    {        Triangle a,b;        scanf("%lf%lf%lf%lf%lf%lf",&a.A.x,&a.A.y,&a.B.x,&a.B.y,&a.C.x,&a.C.y);        scanf("%lf%lf%lf%lf%lf%lf",&b.A.x,&b.A.y,&b.B.x,&b.B.y,&b.C.x,&b.C.y);        if(IsInTriangle(a.A,a.B,a.C,b.A)&&IsInTriangle(a.A,a.B,a.C,b.B)&&IsInTriangle(a.A,a.B,a.C,b.C))        {            printf("contain\n");        }        else if(IsInTriangle(b.A,b.B,b.C,a.A)&&IsInTriangle(b.A,b.B,b.C,a.B)&&IsInTriangle(b.A,b.B,b.C,a.C))        {            printf("contain\n");        }        else if(intersect(a.A,a.B,b.A,b.B)||intersect(a.A,a.B,b.A,b.C)||intersect(a.A,a.B,b.B,b.C))        {            printf("intersect\n");        }        else if(intersect(a.A,a.C,b.A,b.B)||intersect(a.A,a.C,b.A,b.C)||intersect(a.A,a.C,b.B,b.C))        {            printf("intersect\n");        }        else if(intersect(a.B,a.C,b.A,b.B)||intersect(a.B,a.C,b.A,b.C)||intersect(a.B,a.C,b.B,b.C))        {            printf("intersect\n");        }        else        {            printf("disjoint\n");        }    }    return 0;}