AcWing 1091 理想的正方形

#include <bits/stdc++.h>
using namespace std;

const int N = 1010;

int n, m, k;
int w[N][N], res_min[N][N], res_max[N][N];
int a[N], q[N], b[N], c[N];

void get_min(int a[], int b[], int len)
{
    int hh = 0, tt = -1;
    for (int i = 1; i <= len; i ++ )
    {
        if (hh <= tt && q[hh] <= i - k) hh ++;
        while (hh <= tt && a[q[tt]] >= a[i]) tt --;
        q[ ++ tt ] = i;
        b[i] = a[q[hh]];
    }
}

void get_max(int a[], int b[], int len)
{
    int hh = 0, tt = -1;
    for (int i = 1; i <= len; i ++ )
    {
        if (hh <= tt && q[hh] <= i - k) hh ++;
        while (hh <= tt && a[q[tt]] <= a[i]) tt --;
        q[ ++ tt] = i;
        b[i] = a[q[hh]];
    }
}

int main()
{
    scanf("%d%d%d", &n, &m, &k);
    
    for (int i = 1; i <= n; i ++ )
        for (int j = 1; j <= m; j ++ )
            scanf("%d", &w[i][j]);
    
    for (int i = 1; i <= n; i ++ )
    {
        get_min(w[i], res_min[i], m);
        get_max(w[i], res_max[i], m);
    }
    
    int res = INT_MAX;
    for (int i = k; i <= m; i ++ )
    {
        for (int j = 1; j <= n; j ++ ) a[j] = res_min[j][i];
        get_min(a, b, n);
        for (int j = 1; j <= n; j ++ ) a[j] = res_max[j][i];
        get_max(a, c, n);
        for (int j = k; j <= n; j ++ ) res = min(res, c[j] - b[j]);
    }
    printf("%d", res);
    
    return 0;
}