21.03.02 - [BOJ] 10828. 스택

[suhyunsim]

문제

• 10828

핵심 아이디어

• 단순 스택 기능 구현

어려운 점, 실수

• 시간 초과 조심
• 스택 안 쓰고 하는 방법도 있음

풀이

package main.java.com.poogle.BOJ.Q10828;

import java.io.*;
import java.util.Stack;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        Stack<String> stack = new Stack<>();
        while (n-- > 0) {
            String[] command = br.readLine().split(" ");
            switch (command[0]) {
                case "push":
                    stack.push(command[1]);
                    break;
                case "pop":
                    if (!stack.isEmpty()) {
                        System.out.println(stack.pop());
                    } else {
                        System.out.println("-1");
                    }
                    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(stack.peek());
                    } else {
                        System.out.println("-1");
                    }
                    break;
                default:
                    break;
            }
        }
        br.close();
    }
}

package main.java.com.poogle.BOJ.Q10828;

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

public class Main {
    public static int[] stack;
    public static int size = 0;

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb = new StringBuilder();
        StringTokenizer st;
        int N = Integer.parseInt(br.readLine());
        stack = new int[N];
        while (N-- > 0) {
            st = new StringTokenizer(br.readLine(), " ");
            switch (st.nextToken()) {
                case "push":
                    push(Integer.parseInt(st.nextToken()));
                    break;
                case "pop":
                    sb.append(pop()).append('\n');
                    break;
                case "size":
                    sb.append(size()).append('\n');
                    break;
                case "empty":
                    sb.append(empty()).append('\n');
                    break;
                case "top":
                    sb.append(top()).append('\n');
                    break;
            }
        }
        System.out.println(sb);
    }

    public static void push(int item) {
        stack[size] = item;
        size++;
    }

    public static int pop() {
        if (size == 0) {
            return -1;
        } else {
            int res = stack[size - 1];
            stack[size - 1] = 0;
            size--;
            return res;
        }
    }

    public static int size() {
        return size;
    }

    public static int empty() {
        if (size == 0) {
            return 1;
        } else {
            return 0;
        }
    }

    public static int top() {
        if (size == 0) {
            return -1;
        } else {
            return stack[size - 1];
        }
    }
}