백준 10845 큐 구현하기

package practice.algorithm.stackqueue;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.util.ArrayList;import java.util.List;/** * 큐 구현문제 * 20620 kb / 364 ms * ArrayList 사용 * - remove(n) 사용시, 값이 아니라 인덱스를 넣어야 한다. * */public class Bj10845_1 { private static List<Integer> queue = new ArrayList<>(); public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); int num = Integer.parseInt(br.readLine()); for (int i = 0; i < num; i++) { String[] orders = br.readLine().split(" "); run(orders); } } private static void run(String[] orders) { switch (orders[0]) { case "push" : push(Integer.parseInt(orders[1])); break; case "pop" : System.out.println(pop()); break; case "size" : System.out.println(size()); break; case "empty" : System.out.println(empty()); break; case "front" : System.out.println(front()); break; case "back" : System.out.println(back()); break; } } private static int back() { if (empty() != 1) { return queue.get(size()-1); } return -1; } private static int front() { if (empty() != 1) { return queue.get(0); } return -1; } private static int pop() { if (empty() != 1) { int firstIdx = 0; int front = queue.get(firstIdx); queue.remove(firstIdx); return front; } return -1; } private static int empty() { return queue.isEmpty() ? 1 : 0; } private static int size() { return queue.size(); } private static void push(int n) { queue.add(n); }}

package practice.algorithm.stackqueue;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;/** * 큐 구현문제 * 20464 kb / 360 ms * 배열 사용 * */public class Bj10845_2 { private static int frontIdx = 0; private static int backIdx = -1; private static int[] queue; public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); int num = Integer.parseInt(br.readLine()); queue = new int[num]; for (int i = 0; i < num; i++) { String[] orders = br.readLine().split(" "); run(orders); } } private static void run(String[] orders) { switch (orders[0]) { case "push" : push(Integer.parseInt(orders[1])); break; case "pop" : System.out.println(pop()); break; case "size" : System.out.println(size()); break; case "empty" : System.out.println(empty()); break; case "front" : System.out.println(front()); break; case "back" : System.out.println(back()); break; } } private static int back() { if (empty() != 1) { return queue[backIdx]; } return -1; } private static int front() { if (empty() != 1) { return queue[frontIdx]; } return -1; } private static int pop() { if (empty() != 1) { int front = queue[frontIdx]; frontIdx++; return front; } return -1; } private static int empty() { return size() <= 0 ? 1 : 0; } private static int size() { return (backIdx - frontIdx) + 1; } private static void push(int n) { queue[++backIdx] = n; }}