LeetCode 21. Merge Two Sorted Lists

Question

Merge two sorted linked lists and return it as a sorted list. The list should be made by splicing together the nodes of the first two lists.

https://leetcode.com/problems/merge-two-sorted-lists/

• Solution1

class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(0);
        ListNode cur = dummy;
        while(l1 != null && l2 != null){
            if(l1.val < l2.val){
                cur.next = l1;
                l1 = l1.next;
            } else {
                cur.next = l2;
                l2 = l2.next;
            }
           cur = cur.next;
        }
        cur.next = l1 == null ? l2: l1;
        return dummy.next;
    }
}

Complexity:

Time complexity: O(n)

Space complexity: O(1)