HDU2642 Stars 二维树状数组

http://acm.hdu.edu.cn/showproblem.php?pid=2642

裸二维树状数组，题义就是求一块面积内处于发亮状态的星星的个数。

代码如下：

#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <map>
#define MAXN 1005
using namespace std; 

int c[MAXN+5][MAXN+5], N;

bool B[MAXN][MAXN];

inline int lowbit(int x)
{
    return x & -x;
}

inline void modify(int posx, int posy, int val)
{
    for (int i = posx; i <= MAXN; i += lowbit(i))
    {
        for (int j = posy; j <= MAXN; j += lowbit(j))
            c[i][j] += val;
    }
}

inline int getsum(int posx, int posy)
{
    int s = 0;
    for (int i = posx; i > 0; i -= lowbit(i))
    {
        for (int j = posy; j > 0; j -= lowbit(j))
            s += c[i][j];
    }
    return s;
}

inline void swap(int &a, int &b)
{
    int t = a;
    a = b;
    b = t; 
}

inline int deal(int x1, int y1, int x2, int y2)
{
    if (x1 > x2)
        swap(x1, x2);
    if (y1 > y2)
        swap(y1, y2);
    return getsum(x2, y2) - getsum(x1-1, y2) - getsum(x2, y1-1) + getsum(x1-1, y1-1);
}

int main()
{ 
    char op[5];
    int x, y, a, b;
    while (scanf("%d", &N) == 1)
    {
        memset(c, 0, sizeof (c));
        memset(B, 0, sizeof (B));
        for (int i = 1; i <= N; ++i)
        {
            scanf("%s", op);
            if (op[0] == 'B')
            {
                scanf("%d %d", &x, &y);
                x++, y++;
                if (!B[x][y])
                {
                    B[x][y] = true;
                    modify(x, y, 1);
                }
            }
            else if (op[0] == 'D')
            {
                scanf("%d %d", &x, &y);
                x++, y++;
                if (B[x][y])
                {
                    B[x][y] = false;
                    modify(x, y, -1);
                }
            }
            else
            {
                scanf("%d %d %d %d", &a, &x, &b, &y);
                x++, y++, a++, b++;
                printf("%d\n", deal(a, b, x, y));
            }
        } 
    }
    return 0;
}