SPOJ 1029 Matrix Summation【 二维树状数组 】

题意：二维树状数组，更改值的时候有一点不一样，

是将a[x][y]设置为一个值，所以add的时候要将它和以前的值作差一下

#include<iostream>  
#include<cstdio>  
#include<cstring> 
#include <cmath> 
#include<stack>
#include<vector>
#include<map> 
#include<set>
#include<queue> 
#include<algorithm>  
using namespace std;

typedef long long LL;
const int INF = (1<<30)-1;
const int mod=1000000007;
const int maxn=5005;

int a[maxn][maxn];
int c[maxn][maxn];//树状数组
int n;

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

int sum(int x,int y){
    int ret=0;
    int y1;
    while(x > 0){
        y1 = y;
        while(y1 > 0){
            ret += c[x][y1];y1-=lowbit(y1);
        }
        x-=lowbit(x);
    }
    return ret;
}

void add(int x,int y,int d){
    int y1;
    while(x < maxn){
        y1 = y;
        while (y1 < maxn){
            c[x][y1]+=d; y1+=lowbit(y1);
        } 
        x+=lowbit(x);
    }
}

int main(){
    int T;
    scanf("%d",&T);
    while(T--){
        memset(c,0,sizeof(c));
        memset(a,0,sizeof(a));
        scanf("%d",&n);
        char s[15];
        while(scanf("%s",s)!=EOF){
            if(s[0] == 'E') break;
            if(s[1]=='E'){
                int x,y,num;
                scanf("%d %d %d",&x,&y,&num);x++;y++;
                int tmp = num - a[x][y];
                a[x][y] = num;
                add(x,y,tmp); 
            }
            if(s[1]=='U'){
                int x,y,xx,yy;
                int ans=0;
                scanf("%d %d %d %d",&x,&y,&xx,&yy);
                x++;y++;xx++;yy++;
                ans = sum(xx,yy) - sum(x-1,yy) - sum(xx,y-1) + sum(x-1,y-1);
                printf("%d
",ans);
            }
        }    
    }
    return 0;
}