[BaekJoon] 18258번 - 큐 2 [Java][C++]

문제 링크

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1. 문제 풀이

큐 자료구조를 구현하는 문제로 배열을 활용해서 구현했다.

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2. 코드

1. 풀이 [Java]

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

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb = new StringBuilder();
        StringTokenizer st;

        int[] queue = new int[2000000];
        int front = 0;
        int rear = 0;

        int N = Integer.parseInt(br.readLine());
        for (int i = 0; i < N; i++) {
            st = new StringTokenizer(br.readLine());
            String command = st.nextToken();

            if (command.equals("push")) {
                int x = Integer.parseInt(st.nextToken());
                queue[rear++] = x;
            } else if (command.equals("pop")) {
                if (front == rear) {
                    sb.append("-1\n");
                } else {
                    sb.append(queue[front++]).append("\n");
                }
            } else if (command.equals("size")) {
                sb.append(rear - front).append("\n");
            } else if (command.equals("empty")) {
                if (front == rear) {
                    sb.append("1\n");
                } else {
                    sb.append("0\n");
                }
            } else if (command.equals("front")) {
                if (front == rear) {
                    sb.append("-1\n");
                } else {
                    sb.append(queue[front]).append("\n");
                }
            } else {
                if (front == rear) {
                    sb.append("-1\n");
                } else {
                    sb.append(queue[rear - 1]).append("\n");
                }
            }
        }

        System.out.println(sb);
    }
}

2. 풀이 [C++]

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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int queue[2000000];
    int front = 0;
    int rear = 0;

    int n;
    cin >> n;

    for (int i = 0; i < n; i++) {
        string command;
        cin >> command;

        if (command == "push") {
            int x;
            cin >> x;
            queue[rear++] = x;
        } else if (command == "pop") {
            if (front == rear) {
                cout << -1 << '\n';
            } else {
                cout << queue[front++] << '\n';
            }
        } else if (command == "size") {
            cout << rear - front << '\n';
        } else if (command == "empty") {
            if (front == rear) {
                cout << 1 << '\n';
            } else {
                cout << 0 << '\n';
            }
        } else if (command == "front") {
            if (front == rear) {
                cout << -1 << '\n';
            } else {
                cout << queue[front] << '\n';
            }
        } else {
            if (front == rear) {
                cout << -1 << '\n';
            } else {
                cout << queue[rear - 1] << '\n';
            }
        }
    }
}

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