二维树状数组应用

http://poj.org/problem?id=1195

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <vector>
#include <queue>
#include <map>
#include <stack>

using namespace std;

int s;
int p[1030][1030];

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

void add(int a,int b,int d)
{
	for (int i = a; i <= s; i += lowbit(i))
		for (int j = b; j <= s; j += lowbit(j))
		{
			p[i][j] += d;
		}
}

int sum(int a, int b)
{
	int ans = 0;
	for (int i = a; i >0; i -= lowbit(i))
		for (int j = b; j >0; j -= lowbit(j))
		{
			ans += p[i][j];
		}
	return ans;
}

void init(int s)
{
	for (int i = 0; i <= s; i++)
		for (int j = 0; j <= s;j++)
			p[i][j] = 0;
}

int main()
{
		int d;
		while (scanf("%d", &d) != EOF)
		{
			if (d == 3)
				return 0;

			if (d == 0)
			{
				scanf("%d", &s);
				init(s);
			}


			if (d == 1)
			{
				int x, y, a;
				scanf("%d %d %d", &x, &y, &a);
				{
					add(x + 1, y + 1, a);
				}
			}

			if (d == 2)
			{
				int l, b, r, t;
				scanf("%d %d %d %d", &l, &b, &r, &t);
				l++; b++; r++; t++;
				printf("%d\n", sum(l - 1, b - 1) + sum(r, t) - sum(r, b - 1) - sum(l - 1, t));
			}
		}
	return 0;
}

poj-1195