CODEWITHSUNDEEP
javascriptdata-structureslinked-list
BeckiD
BeckiD

Reputation: 315

Linked List contains function returns false, why? JavaScript

Singly linked list javascript implementation. It returns true for the head but all other nodes return false. Why contains method return false? I think something wrong will my add toTail function. But when I'm printing linked list it is giving me all nodes

"use strict";
var LinkedList = function(){
  this.head = null
}
var node = function(value){
  this.value = value;
  this.next = null;
}
LinkedList.prototype.addToHead = function(value){
  var n = new node(value);
  
  if(!this.head){
    this.head = n;
    
  }else{
      this.next = this.head;
      this.head = n;
    }
};


LinkedList.prototype.addToTail = function(value){
  var cur = null;
  var n = new node(value)
  if(!this.head){
    this.head = n;
  }else{
    cur = this.head;
    while(cur.next){
      cur = cur.next;
    }
    cur.next = n;
  }
}

LinkedList.prototype.contains = function(value) {
  var node = this.head;
  while (node) {
    if (node.value === value) {
      return true;
    }
    node = node.next;
  }
  return false;
};

var ll = new LinkedList();
ll.addToTail(20)
ll.addToTail(40)
ll.addToHead(8)
console.log(ll.contains(40))

Upvotes: 0

Views: 1410

Answers (1)

rdubya
rdubya

Reputation: 2916

I think the issue is in your addToHead function. Currently you are losing your list if a head already exists:

"use strict";
var LinkedList = function(){
  this.head = null
}
var node = function(value){
  this.value = value;
  this.next = null;
}
LinkedList.prototype.addToHead = function(value){
  var n = new node(value);
  
  if(!this.head){
    this.head = n;
    
  }else{
      // this.next = this.head; <- What you had
      n.next = this.head; // What it should be
      this.head = n;
    }
};


LinkedList.prototype.addToTail = function(value){
  var cur = null;
  var n = new node(value)
  if(!this.head){
    this.head = n;
  }else{
    cur = this.head;
    while(cur.next){
      cur = cur.next;
    }
    cur.next = n;
  }
}

LinkedList.prototype.contains = function(value) {
  var node = this.head;
  while (node) {
    if (node.value === value) {
      return true;
    }
    node = node.next;
  }
  return false;
};

var ll = new LinkedList();
ll.addToTail(20)
ll.addToTail(40)
ll.addToHead(8)
console.log(ll.contains(40))

Upvotes: 4

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