poj 1410 Intersection

这个题要考虑直线在正方形的内部；顶点给你的顺序不一定就是左上角到右下角；

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<queue>
#include<set>
#include<map>
#include<cstring>
#include<vector>
using namespace std;
class Point
{
public:
      double x,y;
};
class Line
{
public:
      Point A,B;    
};
int dcmp( double x )
{
   if( fabs( x ) < 1.0e-8) return 0;
   if( x  < 0 ) return -1;
   return 1;    
}
bool judge( Point p1, Point p2 ,Point q )
{
    double max_x = p1.x > p2.x ? p1.x : p2.x;
    double min_x = p1.x < p2.x ? p1.x : p2.x;
    double max_y = p1.y > p2.y ? p1.y : p2.y;
    double min_y = p1.y <p2.y ? p1.y : p2.y;
    if( dcmp( q.x - min_x ) >=0 && dcmp( max_x - q.x )>=0 ) 
      if( dcmp( q.y - min_y ) >=0 && dcmp( max_y - q.y )>=0 )
        return true;
    return false;    
}
double multi( Point p1, Point p2 , Point q )
{
   return ( p1.x - q.x )*( p2.y - q.y ) - ( p2.x - q.x )*( p1.y - q.y );
}
bool segment( Line L , Line L1 )
{
   int d1 = dcmp(multi( L.A , L.B , L1.A ));
   int d2 = dcmp(multi( L.A, L.B , L1.B ));
   int d3 = dcmp(multi( L1.A, L1.B ,L.A ));
   int d4 = dcmp(multi( L1.A ,L1.B ,L.B ));
   if( d1*d2 < 0 && d3 *d4 < 0 ) return true;
   if( d1 ==0 && judge( L.A , L.B , L1.A )  ) return true;
   if( d2 ==0 && judge( L.A, L.B , L1.B ) ) return true;
   if( d3 ==0 && judge( L1.A, L1.B ,L.A ) ) return true;
   if( d4 ==0 && judge( L1.A , L1.B ,L.B ) ) return true;
   return false;        
}
bool Solve( Line L , Line Re[] )
{
    for( int i = 0 ; i < 4 ; i ++ )
    {
        if( segment( L ,Re[i] ) )
           return true;    
    }    
    return false;
}
bool judge_again( Line L , Point A[] )
{
    double max_x = A[0].x > A[2].x ? A[0].x :A[2].x;
    double min_x = A[0].x < A[2].x ? A[0].x :A[2].x;
    double max_y = A[0].y > A[2].y ? A[0].y :A[2].y;
    double min_y = A[0].y < A[2].y ? A[0].y :A[2].y;
    if( L.A.x >= min_x && L.A.x <= max_x && L.B.x >= min_x && L.B.x <= max_x)
      if( L.A.y >= min_y && L.A.y <= max_y&&L.B.y >=min_y && L.B.y <= max_y )
          return true;
    return false;
}
bool cmp( Point a , Point b )
{
   if( dcmp( a.x - b.x )==0 ) return a.y < b.y;
   return a.x < b.x;    
}
int main(  )
{
    int n;
    while( scanf( "%d",&n )==1 )
    {
      while( n-- )
      { 
         Line L,Re[4];
         Point A[5];
         scanf( "%lf %lf",&L.A.x,&L.A.y );
         scanf( "%lf %lf",&L.B.x,&L.B.y );
         scanf( "%lf %lf %lf %lf",&A[0].x ,&A[0].y ,&A[2].x,&A[2].y );
         if( A[0].y < A[2].y ) swap( A[0] ,A[2] );
         A[1].x = A[2].x ; A[1].y = A[0].y;
         A[3].x = A[0].x ; A[3].y = A[2].y;
         sort( A , A + 4 ,cmp );
         A[4] = A[0];
         for( int i = 0 ; i < 4 ; i ++ )
         {
             Re[i].A = A[i]; Re[i].B = A[i+1];        
         }
         if( Solve( L , Re ) )
         {            
            printf( "T\n" );    
         }
         else 
         {
            if( judge_again( L ,A ) )
                printf( "T\n" );
            else  printf( "F\n" );
         }                 
      }    
    }
    //system( "pause" );
    return 0;
}