백준 10828번

제목 : 스택

난이도 실버 4

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;


public class Main {

  public static void main(String[] args) throws NumberFormatException, IOException {
    BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
    int n = Integer.parseInt(input.readLine());
    ArrayList<Integer> stack = new ArrayList<Integer>();
    String command = "";
    
   
    
    for(int i =0;i<n; i++){
      command = input.readLine();
      if(command.contains("push")){
        stack.add(Integer.parseInt(command.substring(5)));
      }
      else if(command.contains("pop")){
        if(stack.size()==0)
        {
          System.out.println("-1");
        }
        else{
          System.out.println(stack.get(stack.size()-1));
          stack.remove(stack.size()-1);
        }
       
      }
      else if(command.contains("size")){
        System.out.println(stack.size());
      }
      else if(command.contains("empty")){
        if(stack.isEmpty()==true){
          System.out.println("1");
        }
        else{
          System.out.println("0");
        }
        
      }
      else{
        if(stack.isEmpty()){
          System.out.println("-1");
        }
        else{
          System.out.println(stack.get(stack.size()-1));
        }
        
      }
    }

    }
  }