单调队列（滑动窗口）

#include <iostream>
using namespace std;
using ll = long long;
const int maxn=1e6+10;
int n,k,a[maxn],q[maxn];
int main(){
    ios::sync_with_stdio(false);
    cin>>n>>k;
    for(int i=0;i<n;i++)cin>>a[i];
    int l=0,r=-1;
    for(int i=0;i<n;i++){
        while(l<=r&&i-k+1>q[l])l++;
        while(l<=r&&a[q[r]]>=a[i])r--;
        q[++r]=i;
        if(i>=k-1)cout<<a[q[l]]<<" ";
    }
    cout<<endl;
    l=0,r=-1;
    for(int i=0;i<n;i++){
        while(l<=r&&i-k+1>q[l])l++;
        while(l<=r&&a[q[r]]<=a[i])r--;
        q[++r]=i;
        if(i>=k-1)cout<<a[q[l]]<<" ";
    }
}

　　维护递增序列