BOJ 10828 C++

연결리스트로 구현한 스택

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

class Node {
public:
    Node* link;
    int data;

    Node(int data = 0) : link(nullptr), data(data) {}
};
class Lstack
{
public:
    Node* top;
    Node* cur;

    Lstack()
    {
        top = new Node();
    }

    void push(int data)
    {
        Node* newNode = new Node(data);
        newNode->link = top;
        top = newNode;
    }
    void pop()
    {
        if (top->link != NULL)
        {
            cout << top->data << "\n";
            Node* temp = top;
            top = top->link;
            delete temp;
            return;
        }
        cout << "-1\n";
      
    }
    void empty()
    {
        if (top->link == NULL)
        {
            cout << "1\n";
        }
        else
            cout << "0\n";
    }

    void tap()
    {
        if (top->link == NULL)
            cout << "-1\n";
        else
            cout << top->data << "\n";
    }

    void size()
    {
        int sizeN = 0;
        Node* temp = top;
        while (temp->link != NULL)
        {
           
            temp = temp->link;
            sizeN++;
        }
        cout << sizeN << "\n";
    }
};
int main(void) {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int n; cin >> n;
    Lstack st;
    for (int i = 0; i < n; i++)
    {
        string s; cin >> s;
        if (s == "push")
        {
            int tmp; cin >> tmp;
            st.push(tmp);
        }
        if (s == "top")
        {
            st.tap();
        }
        if (s == "size")
        {
            st.size();
        }
        if (s == "pop")
        {
            st.pop();
        }
        if (s == "empty")
            st.empty();
    }
    return 0;
}