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

const int N = 1000010;
int a[N];

int main() {
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    deque<int> q;
    for (int i = 1; i <= n; i++) {
        while (!q.empty() && a[q.back()] <= a[i]) q.pop_back();
        q.push_back(i);
    }

    while (!q.empty()) {
        cout << a[q.front()] << " ";
        q.pop_front();
    }

    return 0;
}

#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
typedef pair<int,int> aII;  
using ll = long long;
using ULL = unsigned long long;
const int N = 1e6+5;

int n, a[N], q[N];
int hh = 0, tt = -1;
inline void solve() { 
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
    for(int i = 1;i <= n;i++) {
        while (hh <= tt && a[q[tt]] <= a[i]) --tt;
        q[++tt] = i;
    }
    for (int i = hh; i <= tt; i++) cout << a[q[i]] << ' '; 

}
int main() { 
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int _ = 1; 
    //int _; cin >> _;
    while (_--) solve();
    return 0;
}

单调队列板子

#include <bits/stdc++.h>
using namespace std;
const int N = 1000010;
int a[N];
int n;
deque<int> q;
int main(){
    scanf("%d",&n);
    for (int i = 1; i <= n; ++i) {
        scanf("%d",&a[i]);
    }
    for (int i = 1; i <= n; ++i) {
        while(!q.empty() && a[q.back()] <= a[i]) q.pop_back();
        q.push_back(i);
    }
    for (int i = 0; i <= q.size() - 1; ++i) {
        printf("%d ",a[q[i]]);
    }
    return 0;
}