POJ 1195 Mobile phones 二维树状数组

题意：有一个N * N广场，广场里面有一些手机，某个格子是可以改变的，增加或者减少，问一个小矩阵内有多少个手机。
思路：裸的二维树状数组。
代码：
[cpp]
#include <iostream>
#include <cstdio>
#include <string.h>
using namespace std;

typedef long long LL;
const int N = 1030;
int num[N][N];
int lowbit(int x){
    return x & (-x);
}
void update(int x,int y,int add){
    int t = y;
    while(x < N){
       y = t;
       while(y < N){
         num[x][y] += add;
         if(num[x][y] < 0)
             num[x][y] = 0;
         y += lowbit(y);
       }
       x += lowbit(x);
    }
}
LL sum(int x,int y){
    int t = y;
    LL s = 0;
    while(x > 0){
       y = t;
       while(y > 0){
         s += num[x][y];
         y -= lowbit(y);
       }
       x -= lowbit(x);
    }
    return s;
}
int main(){
    //freopen("1.txt","r",stdin);
    int id,n;
    while(scanf("%d%d",&id,&n) != EOF){
        memset(num,0,sizeof(num));
        int x1,y1,x2,y2,value;
        while(1){
          scanf("%d",&id);
          if(id == 3)
              break;
          else if(id == 1){
             scanf("%d%d%d",&x1,&y1,&value);
             update(x1+1,y1+1,value);
          }
          else if(id == 2){
            scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
            printf("%lld\n",sum(x2+1,y2+1) - sum(x1,y2+1) - sum(x2+1,y1) + sum(x1,y1));
          }
        }
    }
    return 0;
}

补充：软件开发 , C++ ,