Merge Two Sorted Linked Lists | Leetcode | Blind 175

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists into one sorted linked list and return the head of the new sorted linked list.

The new list should be made up of nodes from list1 and list2.

Example 1:

Input: list1 = [1,2,4], list2 = [1,3,5]

Output: [1,1,2,3,4,5]

Example 2:

Input: list1 = [], list2 = [1,2]

Output: [1,2]

1. we need to compare between two nodes
2. iterate through the both nodes until one of the node is null

                1 -> 2 -> 4
                1 -> 3 -> 5

const newList = {}
if(currentNode1. val < currentNode2.val){
   newList = currentNode1
   currentNode1 = currentNode1.next
}else{
   newList = currentNode2
   currentNode2 = currentNode2.next
}

To implement this as a code:

/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
var mergeTwoLists = function(list1, list2) {
    let listNode = {
        val: 0,
        next : null
    }
    let currentNode = listNode
    if(!list1){
        return list2
    }

    if(!list2){
        return list1
    }

    while(list1 && list2){
        if(list1.val < list2.val){
            currentNode.next = list1
            list1 = list1.next
        }else{
            currentNode.next = list2
            list2 = list2.next
        }
        currentNode = currentNode.next
    }
    if(list1){
        currentNode.next = list1
    }
     if(list2){
        currentNode.next = list2
    }
    return listNode.next
};