poj 1389 Area of Simple Polygons

离散化处理：

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<queue>
#include<set>
#include<map>
#include<cstring>
#include<vector>
#include<string>
#define LL long long
using namespace std;
class Rec
{
public:
      int x1,y1,x2,y2;    
}rec[1024];
int tx[2024];
bool cmp1( Rec a, Rec b )
{
     return a.y1 < b.y1;    
}
bool cmp2( int a , int b )
{
     return a < b;
}
int Solve( int n , int  cnt )
{
    int s = 0;
    sort( tx , tx + cnt , cmp2 );
    sort( rec , rec + n , cmp1 );
    cnt = unique( tx , tx + cnt ) - tx;
    for( int i = 1 ; i < cnt ; i ++ )
    {
        int l = tx[i-1],r = tx[i],up = -1,down = -1;
        for( int j = 0 ; j <  n ; j ++ )
        {
             if( l >= rec[j].x1 && r <= rec[j].x2 )
             {
                 if( up < rec[j].y1 )
                 {
                     s += ( r - l )*( up - down );
                     up = rec[j].y2 ; down = rec[j].y1;        
                 }
                 else if( up < rec[j].y2 )
                          up = rec[j].y2;        
             }
        }
        s += ( r - l )*( up - down );
    }
    return s;
}
int main(  )
{
    while( 1 )
    {
         int n = 1,cnt = 0;
         scanf( "%d%d%d%d",&rec[0].x1,&rec[0].y1,&rec[0].x2,&rec[0].y2 );
         tx[cnt++] = rec[0].x1 ; tx[cnt++] = rec[0].x2;
         if( rec[0].x1 == -1 ) break;
         
         while( scanf( "%d%d%d%d",&rec[n].x1,&rec[n].y1,&rec[n].x2,&rec[n].y2 ),rec[n].x1 !=-1 )
         {
                tx[cnt++] = rec[n].x1 ; tx[cnt++] = rec[n].x2;
                n++;
//                printf( "n == %d",n );
         }
         printf( "%d\n",Solve( n , cnt ) );    
    }
    //system( "pause" );
    return 0;
}