linkedLIst listnode

import java.util.*;

class ListNode {
  public int value;
  public ListNode next;

  public ListNode(int value){
    this.value = value;
  }
}

class LinkedList {
  public int length = 0;
  public ListNode head;
  public ListNode tail;

  // Time Complexity: O(N)
  // Auxiliary Space Complexity: O()
  public void append(int value){
   //add node to the end
   insert(value, length);
  }


  // Time Complexity: O(N)
  // Auxiliary Space Complexity: O(1)
  public void insert(int value, int index){
    //check to see if index for insertion is out of bounds of the LinkedList
    if(index > length || index < 0){
      return;
    }
    ListNode newNode = new ListNode(value);
    //if no nodes exist, new node is head AND tail
    if(length == 0){
      head = newNode;
      tail = newNode;
    }else if(index == 0){
      //set new node to pt to curr head next
      //set head to pt to new node
      newNode.next = head;
      head = newNode;
    }else if(index == length){
      tail.next = newNode;
      tail = newNode;
    }else{
      //if inserting somewhere in the middle->
      //make iterator node variable and set to head of LinkedList
      ListNode previousNode = head;
      for(int i = 0; i< index-1; i++){
        previousNode = previousNode.next;
      }
      //once node previous to index, insert newNode
      newNode.next = previousNode.next;
      previousNode.next = newNode;
    }
    //increase length to acct for inserted node
    length++;
  }


  // Time Complexity: O(N)
  // Auxiliary Space Complexity: O(1)
   public void delete(int index){

    //out of bounds? return
    if(index < 0 || index >= length){
      return;
    }
    //if there is only 1 item in LinkedList
    if(length == 1){
      head = null;
      tail = null;
    }else if(index == 0){
      head = head.next;
    }else {
      //create iterator
      ListNode previousNode = head;
      for(int i = 0 ; i <index-1; i++){
        previousNode = previousNode.next;
      }
      previousNode.next = previousNode.next.next;
      if(index == length -1){
        tail = previousNode;
      }
    }
    length--;
  }


  // Time Complexity: O(N)
  // Auxiliary Space Complexity: O(1)
  public boolean contains(int value){

  }
}