자료구조- 스택 .java

백준 10828번

 

BufferedReader 와 BufferedWriter로 입출력

* BufferedWriter로 정수를 출력할때 String으로 변환후 출력해야한다. 마지막에는 flush 와 close해야한다!

 

Stack의 push, pop, peek(top), empty, size 

 

import java.util.*;
import java.io.*;
 
public class Main {
    
    public static void main(String[] args) throws Exception {
        
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        
        int n = Integer.parseInt(br.readLine());
        Stack<Integer> stack = new Stack<>();
 
        for(int i =0; i<n; i++) {
            
            StringTokenizer st = new StringTokenizer(br.readLine());
            String str = st.nextToken();
            if(str.equals("push")) {
                int a = Integer.parseInt(st.nextToken());
                stack.push(a);
            }
            else if(str.equals("top")) {
                if(stack.size() > 0) {
                    bw.write(stack.peek() + "");
                }
                else {
                    bw.write(-1 + "");
                }
                bw.write("\n");
                
            }
            else if(str.equals("pop")) {
                if(stack.size() > 0) {
                    bw.write(stack.pop()  + "");
                }
                else {
                    bw.write(-1 + "");
                }
                bw.write("\n");
                
            }
            else if(str.equals("size")) {
                bw.write(stack.size() + "");
                bw.write("\n");
            }
            else if(str.equals("empty")) {
                if(stack.empty()) {
                    bw.write(1 + "");
                }
                else {
                    bw.write(0 + "");
                }
                bw.write("\n");
            }
            
        }
        bw.flush();
        bw.close();
        
 
            
        
    }
    
    
 
}