Merge Two Sorted Lists --leetcode

package com.helloxin.leetcode.algorithms;

import com.helloxin.leetcode.algorithms.preparation.ListNode;

/**
 * create by nandiexin on 2017/12/14
 **/
public class MergeTwoSortedLists {


    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode prehead = new ListNode(-1);

        ListNode prev = prehead;
        while (l1 != null && l2 != null) {
            if (l1.val <= l2.val) {
                prev.next = l1;
                l1 = l1.next;
            } else {
                prev.next = l2;
                l2 = l2.next;
            }
            prev = prev.next;
        }

        // exactly one of l1 and l2 can be non-null at this point, so connect
        // the non-null list to the end of the merged list.
        prev.next = l1 == null ? l2 : l1;
        return  prev.next;
    }

    public static void main(String[] args) {

    }
}

https://github.com/woshiyexinjie/leetcode-xin