HNOI2003 激光炸弹

#include <bits/stdc++.h>

const int max_n=5000+5;

int N,M,Ans;
int sum[max_n][max_n];

inline int read()
{
    register int x=0;
    register char ch=getchar();
    while(!isdigit(ch))
        ch=getchar();
    while(isdigit(ch))
    {
        x=(x<<1)+(x<<3)+ch-‘0‘;
        ch=getchar();
    }
    return x;
}

int main()
{
    int x,y;
    N=read(),M=read();
    for(int i=1;i<=N;++i)
        x=read()+1,y=read()+1,sum[x][y]=read();
    for(int i=1;i<=5000;++i)
        for(int j=1;j<=5000;++j)
            sum[i][j]+=sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1];
    for(int i=M;i<=5000;++i)
        for(int j=M;j<=5000;++j)
            Ans=std::max(Ans,sum[i][j]-sum[i][j-M]-sum[i-M][j]+sum[i-M][j-M]);
    printf("%d\n",Ans);
    return 0; 
}