HDU 1892 See you~

一道二维的树状数组题：这里要注意初始化，

#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;
int c[1024][1024];
int lowbit( int x )
{
    return x & ( -x );
}
void modify( int x, int y , int A  )
{
    for( int i = x ; i <= 1001 ; i += lowbit( i ) )
         for( int j = y ; j <= 1001 ; j += lowbit( j ) )
              c[i][j] += A;    
}
int Sum( int x, int y  )
{
   int sum = 0;
   for( int i = x ; i > 0 ; i -= lowbit( i ) )
        for( int j = y ; j > 0 ; j -= lowbit( j ) )
             sum += c[i][j];
   return sum;    
}
void Init(  )
{
   memset( c , 0 , sizeof( c ) );
   for( int i = 1 ; i <= 1001 ; i ++ )
        for( int j = 1 ; j<= 1001 ; j ++ )
            c[i][j] = lowbit(i)*lowbit(j);
}
int main(  )
{
    int T,x1,y1,x2,y2,n,A,sum;     
    char str[3];
    while( scanf( "%d",&T )==1 )
    {
         for( int i = 1 ; i <=T ;i ++ )
         {              
              Init(  );
              scanf( "%d",&n );
              printf( "Case %d:\n",i );
              for( int j = 0 ; j < n ; j ++ )
              {
                   scanf( "%s",str );
                   switch( str[0] )
                   {
                     case 'S': scanf( "%d %d %d %d",&x1,&y1,&x2,&y2 );
                               if( x1 > x2 ) swap( x1 ,x2 ); if( y1 > y2 ) swap( y1 ,y2 );
                               sum = Sum(x2+1,y2+1)+Sum(x1,y1)-Sum(x1,y2+1)-Sum(x2+1,y1);
                                 printf( "%d\n",sum );
                                 break;
                     case 'A': scanf( "%d %d %d",&x1,&y1 ,&A );
                                modify( x1+1 ,y1+1 ,A  ); break;
                     case 'D': scanf( "%d %d %d",&x1,&y1,&A );
                                sum = Sum(x1+1,y1+1)+Sum(x1,y1)-Sum(x1,y1+1)-Sum(x1+1,y1 );
                                A = min( sum ,A );
                                modify( x1+1 , y1+1, -A ); break;
                     case 'M':  scanf( "%d %d %d %d %d",&x1,&y1,&x2,&y2,&A );
                                sum = Sum(x1+1,y1+1)+Sum(x1,y1)-Sum(x1,y1+1)-Sum(x1+1,y1);
                                A = min( sum ,A );
                                modify( x1 + 1, y1 + 1, -A );
                                modify( x2 +1 , y2 + 1, A ); break;
                   }        
              }        
         }    
    }
    //system( "pause" );
    return 0;
}