合并两个有序链表

知识点： 链表指针的指向。

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        
        ListNode head = new ListNode(0);
        ListNode  cur = head;
        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;
        }
        if( l1 != null ){
            cur.next = l1;
        }
        if( l2 != null ){
            cur.next = l2;
        }
        
        return head.next;
    }
}