Leetcode - Merge Two Sorted Lists

Merge Two Sorted Lists

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

Solution:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if(l1 == null || l2 == null)    return l1 == null ? l2 : l1;
        
        // init
        ListNode head;
        if(l1.val < l2.val) {
            head = new ListNode(l1.val);
            l1 = l1.next;
        }
        else {
            head = new ListNode(l2.val);
            l2 = l2.next;
        }
        ListNode node = head;
        
        // loop
        while(l1 != null && l2 != null) {
            if(l1.val < l2.val) {
                node.next = new ListNode(l1.val);
                node = node.next;
                l1 = l1.next;
            }
            else {
                node.next = new ListNode(l2.val);
                node = node.next;
                l2 = l2.next;
            }
        }
        
        while(l1 != null) {
            node.next = new ListNode(l1.val);
            node = node.next;
            l1 = l1.next;
        }
        
        while(l2 != null) {
            node.next = new ListNode(l2.val);
            node = node.next;
            l2 = l2.next;
        }
        
        return head;
    }
}