[알고리즘] Queue

[알고리즘] Queue

Queue

public class Queue {
 
    public static int front = -1;
    public static int rear = -1;
    public static int[] q = new int[5];
    
    public static boolean isFull() {
        return rear == q.length -1;
    }
    public static boolean isEmpty() {
        return front == rear;
    }
    
    public static void enQueue(int item) {
        if(isFull()) {
            System.out.println("가득 찼음");
        } else {
            System.out.println(item + "추가");
            q[++rear] = item;
        }
    }
    
    public static int deQueue() { 
        if(isEmpty()) {
            System.out.println("비어 있음");
            return -1;
        } else {
            System.out.println("삭제");
            return q[++front];
        }
    }
    public static void main(String[] args) {
            
        enQueue(1);
        enQueue(2);
        enQueue(3);
        deQueue();
        deQueue();
        deQueue();
        deQueue();
        
    }
 
}

원형 Queue

public class 원형Queue {
 
    public static int front = 0;
    public static int rear = 0;
    public static int[] q = new int[5];
    
    public static boolean isFull() {
        return (rear+1) % q.length == front;
    }
    public static boolean isEmpty() {
        return front == rear;
    }
    
    public static void enQueue(int item) {
        if(isFull()) {
            System.out.println("가득 찼음");
        } else {
            System.out.println(item + "추가");
            rear++;
            if(rear == q.length) {
                rear = 0;
            }
            q[rear] = item;
        }
    }
    
    public static int deQueue() { 
        if(isEmpty()) {
            System.out.println("비어 있음");
            return -1;
        } else {
            System.out.println("삭제");
            front++;
            if ( front == q.length ) {
                front = 0;
            }
            return q[front];
        }
    }
    public static void main(String[] args) {
            
        enQueue(1);
        enQueue(2);
        enQueue(3);
        deQueue();
        deQueue();
        deQueue();
        deQueue();
        
    }
 
}

연결 Queue

import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
 
public class 연결Queue {
 
    public static Node front = null;
    public static Node rear = null;
    
    //public static boolean isFull() { 
    //}
    
    public static boolean isEmpty() {
        return front == null;
    }
    
    public static void enQueue(int item) {
        Node newNode = new Node(item);
        if (isEmpty()) { // 공백 큐 였으면
            front = newNode;
            rear = newNode;
        } else {
            rear.link = newNode;
            rear = newNode;
        }
    }
    
    public static int deQueue() { 
        if (isEmpty()) {
            System.out.println("Queue underflow Error~");
            return -1;
        } else {
            int data = front.data;
            front = front.link;
            if(isEmpty()) { // 공백 큐라면
                rear = null;
            }
            return data;
        }
    }
    
    
    
    public static void main(String[] args) {
        
        Queue<Integer> q = new LinkedList<Integer>();
        
        enQueue(1);
        enQueue(2);
        enQueue(3);
        System.out.println(deQueue());
        System.out.println(deQueue());
        System.out.println(deQueue());
        System.out.println(deQueue());
    }
}
 
class Node {
    Node link; // 다음 노드의 주소를 저장할 변수
    int data;
    
    public Node(int data) {
        this.data = data;
    }
}