MergeTwoLinkedList

ID: 21

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

Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

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

Idea

While loop, value comparison; Dummy head

Start from the smaller head, while loop to check if any of the list turns null

Compare and insert

Code

public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode dummy = new ListNode();
        ListNode result = dummy;
        while(list1 != null && list2 != null){
            if (list1.val < list2.val){
                dummy.next = new ListNode(list1.val);
                list1 = list1.next;
            }else{
                dummy.next = new ListNode(list2.val);
                list2 = list2.next;
            }
            dummy = dummy.next;
        }
        dummy.next =(list1!=null)?list1:list2;
        return result.next;
    }