HDU 2642 Stars

HDU 2642 Stars

二维树状数组的应用。每次在某个点上增加一个值，或是询问某块区域内的和。
以下是我的代码：

#include < iostream >
#include < string >
#include < algorithm >
#include < cstdio >
#include < cstring >
#define  lowbit(x) ((x)&(-(x)))
using   namespace  std;
const   int  n( 1001 );

int  bit[n + 7 ][n + 7 ];
bool  bright[n + 7 ][n + 7 ];

void  Add( int  x, int  y, int  delta)
{
     for ( int  i = x;i <= n;i += lowbit(i))
         for ( int  j = y;j <= n;j += lowbit(j))
            bit[i][j] += delta;
}

int  Sum( int  x, int  y)
{
     int  re( 0 );
     for ( int  i = x;i > 0 ;i -= lowbit(i))
         for ( int  j = y;j > 0 ;j -= lowbit(j))
            re += bit[i][j];
     return  re;
}

int  main()
{
    memset(bit, 0 , sizeof (bit));
    memset(bright, false , sizeof (bright));

     int  m;
    cin >> m;
     while (m -- )
    {
         string  cmd;
        cin >> cmd;
         if (cmd == " B " )
        {
             int  x,y;
            scanf( " %d%d " , & x, & y);
            x ++ ;y ++ ;
             if ( ! bright[x][y])
                Add(x,y, 1 );
            bright[x][y] = true ;
        }
         else   if (cmd == " D " )
        {
             int  x,y;
            scanf( " %d%d " , & x, & y);
            x ++ ;y ++ ;
             if (bright[x][y])
                Add(x,y, - 1 );
            bright[x][y] = false ;
        }
         else   if (cmd == " Q " )
        {
             int  x1,y1,x2,y2;
            scanf( " %d%d%d%d " , & x1, & x2, & y1, & y2);
            x1 ++ ;y1 ++ ;x2 ++ ;y2 ++ ;
             if (x1 > x2)
                swap(x1,x2);
             if (y1 > y2)
                swap(y1,y2);
            printf( " %d\n " ,Sum(x2,y2) - Sum(x1 - 1 ,y2) - Sum(x2,y1 - 1 ) + Sum(x1 - 1 ,y1 - 1 ));
        }
    }

     return   0 ;
}