0021. Merge Two Sorted Lists

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

Description

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.

Example 1:

**Input:** l1 = [1,2,4], l2 = [1,3,4]
**Output:** [1,1,2,3,4,4]

Example 2:

**Input:** l1 = [], l2 = []
**Output:** []

Example 3:

**Input:** l1 = [], l2 = [0]
**Output:** [0]

Constraints:

• The number of nodes in both lists is in the range [0, 50].

• -100 <= Node.val <= 100

• Both l1 and l2 are sorted in non-decreasing order.

ac

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