COI road cube

#include<stdio.h>
#include<queue>
using namespace std;
int main()
{
    int n,m,k;
    scanf("%d %d %d",&n,&m,&k);
    int board[n+1][m+1];

    for(int i = n ; i >= 1 ; i --){
        for(int j = 1 ; j <= m ; j ++){
            scanf("%d",&board[i][j]);
        }
    }

    int dp[m+1];
    int ndp[m+1];
    for(int i = 1 ; i <= m ; i ++){
        dp[i] = board[1][i];
    }
    priority_queue<pair<int,int>/* ,vector<pair<int,int> > ,greater<pair<int,int> > */ > pq;

    for(int i = 2 ; i <= n ; i ++){
        for(int j = 1 ; j <= k + 1 ; j ++){
            pq.push({dp[j],j});
        }
        for(int j = 1 ; j <= m ; j ++){
            while(!pq.empty() && pq.top().second < j - k)pq.pop();
            ndp[j] = board[i][j] + pq.top().first;
            if(j+k+1 <= m)pq.push({dp[j+k+1],j+k+1});
        }
        while(!pq.empty())pq.pop();
        for(int j = 1 ; j <= m ; j ++){
            dp[j] = ndp[j];
        }
    }
    int ans = 0;
    for(int i = 1 ; i <= m ; i ++){
        if(dp[i] > ans)ans = dp[i];
    }
    printf("%d",ans);
    return 0;
}