I'm doing a CodeFights problem, trying to remove elements from a singly linked list that has the value k.

Below is what I have (l is the list and k is the value):

function removeKFromList(l, k) {
    //figure out the head of the new list so we can reference it later
    var head = l;

    while (head.value === k){
        head = head.next;
    }

    var node = head;
    var temp = null;

    while (node && node !== null) {
        if (node.next.value === k){
            temp = node.next.next;
            node.next.next = null;
            node.next = temp;
        }
        node = node.next; 
        console.log("+++", head)
    }

    console.log("---", head)  
}

The CodeFight test cast is 3 -> 1 -> 2 -> 3 -> 4 -> 5. The final result would have been 1 -> 2 -> 4 -> 5. But my '---' console log keeps returning "Empty" (according to the CodeFights console).

My '+++' console log returns the correct head with element each loop.

I've been pulling my hair out over this, any idea what is missing here?

I'm doing a CodeFights problem, trying to remove elements from a singly linked list that has the value k.

Below is what I have (l is the list and k is the value):

function removeKFromList(l, k) {
    //figure out the head of the new list so we can reference it later
    var head = l;

    while (head.value === k){
        head = head.next;
    }

    var node = head;
    var temp = null;

    while (node && node !== null) {
        if (node.next.value === k){
            temp = node.next.next;
            node.next.next = null;
            node.next = temp;
        }
        node = node.next; 
        console.log("+++", head)
    }

    console.log("---", head)  
}

The CodeFight test cast is 3 -> 1 -> 2 -> 3 -> 4 -> 5. The final result would have been 1 -> 2 -> 4 -> 5. But my '---' console log keeps returning "Empty" (according to the CodeFights console).

My '+++' console log returns the correct head with element each loop.

I've been pulling my hair out over this, any idea what is missing here?

• javascript
• algorithm
• linked-list
• closures
• singly-linked-list

• please add the example of the list es well, as the call of the function with values. – Nina Scholz Commented Dec 9, 2017 at 18:57
• I included to test case. The list is already given as a SLL so I wouldn't have to create one. Hope this helps – Kaisin Li Commented Dec 9, 2017 at 19:12
• 1 one problem is the first node, you need to assign the next node as start of the list. this works only of the list is supplied via an object. – Nina Scholz Commented Dec 9, 2017 at 19:16
• 1 Your while loop condition should be while (node && node.next != null). – David G Commented Dec 9, 2017 at 19:17

4 Answers 4

You need to return the list if you delete the first node.

Then you need a loop for taking the next not while the value is not found.

At last you need a check if the last node exist and if the value is found, then assign the next node to the last next property.

function removeNode(list, value) {
    var node = list,
        last;

    if (node && node.value === value) {
        return node.next;
    }

    while (node && node.value !== value) {
        last = node,
        node = node.next;
    }
    if (last && node.value === value) {
        last.next = node.next;
    }
    return list;
}

var list = { value: 1, next: { value: 2, next: { value: 3, next: { value: 4, next: { value: 5, next: { value: 6, next: { value: 7, next: null } } } } } } };

list = removeNode(list, 5);
console.log(list)

list = removeNode(list, 1);
console.log(list)

list = removeNode(list, 7);
console.log(list)

.as-console-wrapper { max-height: 100% !important; top: 0; }

Try this:

function myRemove(l, k){
    if(l == null){
        return l;
    }
    while(l.value == k){
        l = l.next;
    }
    thisNode = l;
    nextNode = thisNode.next;
    while(nextNode != null){
        if(nextNode.value == k){
            thisNode.next = nextNode.next;
            // No more nodes, ie last node was to be removed
            if(thisNode.next == null)
                break;
        }
        thisNode = thisNode.next;
        nextNode = thisNode.next;       
    }
    return l;
}

This could be also done by recursion:

 function removeKFromList({value, next}, k) {       
   if(value === k){
      return next ? removeKFromList(next, k) : null;
   } else {
      return {
        next : removeKFromList(next, k),
        value
       };
  }
 }

Easy to understand solution :

remove(index) { 
if (index < 0 || index > this.length) return undefined 
if (index === 0) return this.shift() 
if (index === this.length - 1) return this.pop() 
let previousNode = this.get(index - 1) 
let removed = previousNode.next 
previousNode.next = removed.next 
previousNode.next = currentNode.next    
this.length-- 
return removed 
} 

get(index) { 
if (index < 0 || index >= this.length) return null 
let current = this.head 
let count = 0 
while (count !== index) { 
current = current.next 
count++ 
} 
return current 
} 

pop() { 
if (!this.head) return undefined 
let current = this.head 
let newTail = current
while (current.next) { 
newTail = current 
current = current.next 
} 
this.tail = newTail 
this.tail.next = null 
this.length-- 
if (this.length === 0) { 
this.head = null 
this.tail = null 
} 
return current 
} 
 

shift() { 
if (!this.head) return undefined 
let currentHead = this.head 
this.head = current.next 
this.length-- 
if (this.length === 0) { 
this.tail = null 
} 

return currentHead 

}