(模拟队列) $O(n)$

C++ 代码

#include <iostream>
#include <vector>
using namespace std;

vector<int> vec;
const int N = 1000010;
int q[N], hh = 0, tt = 0;
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int num, k, temp;
    cin >> num >> k;
    for(int i = 0; i < num; i++)
    {
        cin >> temp;
        vec.push_back(temp);
    }

    for(int i = 0; i < num; i++)
    {
        if(hh != tt && i - q[hh] >= k) hh++;
        while(hh != tt && vec[i] <= vec[q[tt-1]]) tt--;
        q[tt++] = i;
        if(i >= k-1) cout << vec[q[hh]] << " ";
    }
    cout << endl;
    hh = 0, tt = 0;
     for(int i = 0; i < num; i++)
    {
        if(hh != tt && i - q[hh] >= k) hh++;
        while(hh != tt && vec[i] >= vec[q[tt-1]]) tt--;
        q[tt++] = i;
        if(i >= k-1) cout << vec[q[hh]] << " ";
    }

    return 0;
}