[日常摸鱼]bzoj1218[HNOI2003]激光炸弹-二维前缀

#include<cstdio>
#define rep(i,n) for(register int i=1;i<=n;i++)
#define REP(i,a,b) for(register int i=a;i<=b;i++)
const int N=5005;
int n,r,w[N][N],x,y,v,p,q,ans;
inline int max(int a,int b){return a>b?a:b;}
int main()
{
    scanf("%d%d",&n,&r);p=q=r;
    rep(i,n){scanf("%d%d%d",&x,&y,&v);x++;y++;w[x][y]=v;p=max(p,x);q=max(q,y);}
    rep(i,p)rep(j,q)w[i][j]=w[i][j]+w[i-1][j]+w[i][j-1]-w[i-1][j-1];
    REP(i,r,p)REP(j,r,q)ans=max(ans,w[i][j]-w[i-r][j]-w[i][j-r]+w[i-r][j-r]);
    printf("%d",ans); 
    return 0;
}