poj 1654 Area

求多边形的面积；

#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:
      int x,y;    
}point[1000024],d[10];

Point Get_point( Point a, int num )
{
    Point b;
    b.x = a.x + d[num].x;
    b.y = a.y + d[num].y;
    return b;    
}
int multi( Point p1, Point p2 , Point q )
{
   return ( p1.x - q.x )*( p2.y - q.y ) - ( p2.x - q.x )*( p1.y - q.y );
}
void Initial( )
{
    d[1].x = -1; d[1].y = -1;
    d[2].x = 0 ; d[2].y = -1;
    d[3].x = 1 ; d[3].y = -1;
    d[4].x = -1; d[4].y = 0;
    d[6].x = 1 ; d[6].y = 0;
    d[7].x = -1; d[7].y = 1;
    d[8].x = 0 ; d[8].y = 1;
    d[9].x = 1 ; d[9].y = 1;    
};
int main(  )
{
   int n;
   Initial();
   char str[1000024];
   while( scanf( "%d",&n )==1 )
   {
      while( n-- )
      {
          int i = 1;
          scanf( "%s",str + 1 );
          point[0].x = 0 ; point[1].y = 0;
          while( str[i]!='5' )
          {
             point[i] = Get_point( point[i-1] , str[i]-'0' );    
             i++;
          }    
          double ans = 0;
          for( int j = 1 ; j < i -1 ; j++ )
          {
               ans += multi( point[j] ,point[j+1],point[0]);    
          }
          ans = fabs( ans/2 );
          if( fabs(ans - ( long long  )ans) < 1.0e-8  )    
          printf( "%.0f\n",ans );
          else printf( "%.1f\n",ans );
      }        
   }
    //system( "pause" );
    return 0;
}