첫 시도
- java에서 큐는 리스트로 구현되어 있다
- LinkedList를 사용해서 구현
해결
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import java.io.*;
import java.lang.reflect.Array;
import java.util.*;
public class Main {
public static void main(String[] ars) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringBuilder sb = new StringBuilder();
int N = Integer.parseInt(br.readLine());
LinkedListQueue q = new LinkedListQueue();
for (int i = 0; i < N; i++) {
String[] input = br.readLine().split(" ");
String commend = input[0];
switch (commend){
case "push":
int num = Integer.parseInt(input[1]);
q.push(num);
break;
case "pop":
sb.append(q.pop()).append("\n");
break;
case "size":
sb.append(q.size()).append("\n");
break;
case "empty":
sb.append(q.empty()).append("\n");
break;
case "front":
sb.append(q.front()).append("\n");
break;
case "back":
sb.append(q.back()).append("\n");
break;
}
}
System.out.println(sb.toString());
}
}
class Node{
int data;
Node next;
public Node(int data) {
this.data = data;
this.next = null;
}
}
class LinkedListQueue{
Node head;
Node tail;
int size;
public LinkedListQueue() {
this.head = null;
this.tail = null;
this.size = 0;
}
public void push(Integer x){
Node nNode = new Node(x);
if(size == 0){
head = nNode;
}
else{
tail.next = nNode;
}
tail = nNode;
size++;
}
public int pop(){
int result = -1;
if(size != 0){
result = head.data;
head = head.next;
size--;
}
return result;
}
public int size(){
return size;
}
public int empty(){
int result = 1;
if(size != 0){
result = 0;
}
return result;
}
public int front(){
int result = -1;
if(size != 0){
result = head.data;
}
return result;
}
public int back(){
int result = -1;
if(size != 0){
result = tail.data;
}
return result;
}
}