C++ 代码

#include<iostream>

using namespace std;

const int N = 1e5 + 10;

int stack[N], tt;

void push(int x)
{
    stack[tt++] = x;
}

void pop()
{
    tt--;
}

int top()
{
    return stack[tt - 1];
}

bool empty()
{
    return tt == 0;
}

int main()
{
    int n;
    cin >> n;

    while (n--)
    {
        int x;
        cin >> x;

        if (empty())
        {
            push(x);
            cout << -1 << " ";
            continue;
        }
        else
        {
            if (x <= top())
            {
                while (x <= top() && !empty())pop();
                empty() ? cout << -1 << " " : cout << top() << " ";
                push(x);
            }
            else cout << top() << " " , push(x);
        }

    }

    return 0;
}