二维树状数组（HD2642）

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;

#define BITMAX     1002    //数组大小
typedef int valueType;    //元素类型定义
valueType BITree[BITMAX][BITMAX];    //二维树状数组，初始化
/* 2^k k表示节点编号 x 二进制末尾 0 的个数 */
inline int lowbit(int x)
{
    return x & (-x);
}

/* 节点编号不能为 0 */
/* 二维 C[x][y] = sum(A[i][j]) 其中，x-lowbit[x]+1 <= i<=x 且 y-lowbit[y]+1 <= j <=y */
inline void addPoint(int x, int y, valueType add, int n)
{
    for (int i = x; i <= n; i += lowbit(i))
        for (int j = y; j <= n; j += lowbit(j))
            BITree[i][j] += add;
}
inline valueType readSum(int x, int y)
{
    valueType sum = 0;
    for (int i = x; i > 0; i -= lowbit(i))
        for (int j = y; j > 0; j -= lowbit(j))
            sum += BITree[i][j];
    return sum;
}

bool f[BITMAX][BITMAX];
int main()
{
    int m;
    char cc[2];
    int a, b, c, d;
    scanf("%d", &m);
    memset(BITree, 0, sizeof(BITree));
    memset(f, false, sizeof(f));
    while (m--){
        scanf("%s", &cc);
        switch (cc[0])
        {
        case 'B':
            scanf("%d %d", &a, &b);
            ++a; ++b;
            if (f[a][b]) break;
            addPoint(a, b, 1, BITMAX);
            f[a][b] = true;
            break;
        case 'D':
            scanf("%d %d", &a, &b);
            ++a; ++b;
            if (f[a][b]) addPoint(a, b, -1, BITMAX);
            f[a][b] = false;
            break;
        case 'Q':
            scanf("%d %d %d %d", &a, &b, &c, &d);
            ++a; ++b; ++c; ++d;
            if (a > b) swap(a, b);
            if (c > d) swap(c, d);
            printf("%d
", readSum(b, d) - readSum(b, c - 1) - readSum(a - 1, d) + readSum(a - 1, c - 1));
            break;
        default:
            break;
        }
    }
}