数组前缀和

nt main()
{
    while(scanf("%d%d",&n,&r)!=EOF)
    {
        memset(f,0,sizeof(f));
        for(int i=1;i<=n;i++)
        {
            scanf("%d%d%d",&x,&y,&z);
            f[x+1][y+1]=z;
        }
        for(int i=1;i<=5001;i++)
            for(int j=1;j<=5001;j++)
                f[i][j]+=f[i-1][j]+f[i][j-1]-f[i-1][j-1];
        int ans=0;
        for(int i=r;i<=5001;i++)
            for(int j=r;j<=5001;j++)
                ans=max(ans,f[i][j]-f[i-r][j]-f[i][j-r]+f[i-r][j-r]);
        printf("%d\n",ans);
    }
    return 0;
}