二维树状数组
題目:http://poj.org/problem?id=1656
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#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; }
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