[Algorithm] 백준 단계별로 풀어보기 - 단계 15. 스택

스택 사용하기

10828. 스택

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Stack;
import java.util.StringTokenizer;

public class BOJ_10828 {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;
        int N = Integer.parseInt(br.readLine());

        Stack<Integer> stack = new Stack<>();
        for(int i=0; i<N; i++) {
            st = new StringTokenizer(br.readLine());
            String str = st.nextToken();

            switch (str) {
                case "push":
                    stack.push(Integer.parseInt(st.nextToken()));
                    break;
                case "pop":
                    if(stack.isEmpty()) System.out.println("-1");
                    else System.out.println(stack.pop());
                    break;
                case "size":
                    System.out.println(stack.size());
                    break;
                case "empty":
                    if(stack.isEmpty()) System.out.println("1");
                    else System.out.println(0);
                    break;
                case "top":
                    if(stack.isEmpty()) System.out.println("-1");
                    else System.out.println(stack.peek());
                    break;
            }
        }
    }
}

10773. 제로

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Stack;

public class BOJ_10773 {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int N = Integer.parseInt(br.readLine());

        Stack<Integer> stack = new Stack<>();
        for(int i=0; i<N; i++) {
            int num = Integer.parseInt(br.readLine());
            if(num == 0) {
                stack.pop();
            } else {
                stack.push(num);
            }
        }

        int size = stack.size(), sum = 0;
        for(int i=0; i<size; i++) {
            sum += stack.pop();
        }
        System.out.print(sum);
    }
}