알고리즘_LinkedList(리스트)

2022년 11월 6일 코딩 스터디를 진행하며 LinkedList의 방식을 직접 구현한 것입니다.

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package linkedList;

public class Main {
   public static void main(String[] args) {
      LinkedList numbers = new LinkedList();
      numbers.addLast(10);
      numbers.addLast(20);
      numbers.addLast(30);
      numbers.add(2,25);
      System.out.println(numbers.toString());
      numbers.remove(2);
      System.out.println(numbers.toString());
      System.out.println(numbers.get(0));
      System.out.println("size: "+numbers.size());
   }
}

---

package linkedList;

public class LinkedList {
   private Node head;
   private Node tail;
   private int size = 0;
   private class Node{
      private Object data;
      private Node next;
      public Node(Object input) {
         this.data = input;
         this.next = null;
      }
      public String toString() {
         return String.valueOf(this.data);
      }
   }
   
   public void addFirst(Object input) {
      Node newNode = new Node(input);
      newNode.next = head;
      head = newNode;
      size++;
      if(head.next==null) {
         tail = head;
      }
   }
   
   public void addLast(Object input) {
      Node newNode = new Node(input);
      if(size==0) {
         addFirst(input);
      }else {
         tail.next = newNode;
         tail = newNode;
         size++;
      }
   }
   
   public Node node(int index) {
      Node x = head;
      for(int i=0;i<index;i++) {
         x = x.next;
      }
      return x;
   }
   
   public void add(int k, Object input) {
      if(k==0) {
         addFirst(input);
      }else {
         Node temp1 = node(k-1);
         Node temp2 = temp1.next;
         Node newNode = new Node(input);
         temp1.next = newNode;
         newNode.next = temp2;
         size++;
      }
   }
   
   public void removeFirst() {
      Node temp = head;
      head = head.next;
      temp = null;
   }
   
   public void remove(int index) {
      if(index==0) {
         removeFirst();
      }else {
         Node temp = node(index-1);
         Node tobeDeleted = temp.next;
         temp.next = tobeDeleted.next;
         if(tobeDeleted == tail) {
            tail = temp;
         }
         tobeDeleted = null;
         size--;
      }
   }
   
   public Object get(int index) {
      Node x = node(index);
      return x.data;
   }
   
   public int size() {
      return this.size;
   }
   
   public String toString() {
      if(head == null) {
         return "[]";
      }
      Node temp = head;
      String str = "[";
      while(temp.next != null) {
         str += temp.data + ", ";
         temp = temp.next;
      }
      str += temp.data; // tail 값 넣어주기
      return str+"]";
   }
}