Merge Two Sorted Lists

Leetcode 21.

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
      if(l1 == null)
        return l2;
      if(l2 == null)
        return l1;
     if(l1.val < l2.val){
        l1.next = mergeTwoLists(l1.next,l2);
        return l1; 
     }else{
        l2.next = mergeTwoLists(l1,l2.next);
        return l2; 
     }
    }
}