二维树状数组

题目：http://poj.org/problem?id=1656

 

#include <iostream>
#include <string.h>
#include <stdio.h>

using namespace std;
const int N = 205;

int flag[N][N];
int c[N][N];

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

void Update(int x,int y,int color)
{
    if(color==flag[x][y]) return;
    flag[x][y]=color;
    for (int i=x; i<=N; i+=Lowbit(i))
        for(int j=y; j<=N; j+=Lowbit(j))
            c[i][j]+=color;
}

int getSum(int x,int y)
{
    int ans = 0;
    for(int i=x; i>0; i-=Lowbit(i))
        for(int j=y; j>0; j-=Lowbit(j))
            ans += c[i][j];
    return ans;
}

int main()
{
    int t;
    char str[10];
    scanf("%d",&t);
    memset(c,0,sizeof(c));
    memset(flag,-1,sizeof(flag));
    while(t--)
    {
        int x,y,l;
        scanf("%s%d%d%d",str,&x,&y,&l);
        if(str[0] == 'T')
        {
            printf("%d\n",getSum(x+l-1,y+l-1)-getSum(x+l-1,y-1)-getSum(x-1,y+l-1)+getSum(x-1,y-1));
            continue;
        }
        int val = 1;
        if(str[0] == 'W') val = -val;
        for(int i=x; i<=x+l-1; i++)
            for(int j=y; j<=y+l-1; j++)
                Update(i,j,val);
    }
    return 0;
}