bzoj1218 激光炸弹 二维前缀和

    直接暴力做前缀和，再暴力枚举右下节点即可，注意常数。

下附AC代码：

#include <cstdio>#include <iostream>#include <cstring>#include <cmath>using namespace std;int a[5010][5010]={0};int main(){int n,r;scanf("%d%d",&n,&r);int i,j,ans=0;for (i=1; i<=n; i++){int u,v,c; scanf("%d%d%d",&u,&v,&c);a[u+1][v+1]+=c;}for (i=1; i<=5001; i++)for (j=1; j<=5001; j++) a[i][j]+=a[i-1][j];for (i=1; i<=5001; i++)for (j=1; j<=5001; j++) a[i][j]+=a[i][j-1];for (i=r; i<=5001; i++)      for (j=r; j<=5001; j++)        ans=max(ans,a[i][j]+a[i-r][j-r]-a[i][j-r]-a[i-r][j]);    printf("%d",ans);return 0;}

2015.2.20

by lych