Merge Two Sorted Lists

#javascript #algorithms #interview #career

Question: Given two sorted linked lists, merge them!

eg:


List 1 : 1 -> 3 -> 5
List 2 : 2 -> 4 -> 6

Merged list: 1 -> 2 -> 3 -> 4 -> 5 -> 6

If you've solved merge sort before, the approach is similar to that but here we have to play pointers. So let's play with them!

Algorithm :


var mergeTwoLists = function(l1, l2) {
    let dummy = new ListNode(-1);
    let head = dummy;
    while(l1!= null && l2 != null){
        if(l1.val<l2.val){
            head.next = l1;
            l1 = l1.next;
        }else{
            head.next = l2;
            l2 = l2.next;
        }
        head = head.next;
    }

    if(l1 != null){
        head.next = l1;
    }

    if(l2 != null){
        head.next = l2;
    }

    return dummy.next;
};