题目链接：合并两个排序的链表

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pHead1 ListNode类 
     * @param pHead2 ListNode类 
     * @return ListNode类
     */
    public ListNode Merge (ListNode l1, ListNode l2) {
        // write code here
        ListNode dummy = new ListNode(-1);

        ListNode cur = dummy;

        while(l1 != null && l2 != null)
        {
            if(l1.val < l2.val)
            {
                cur = cur.next = l1;
                l1 = l1.next;
            }
            else {
                cur = cur.next = l2;
                l2 = l2.next;
            }
        }
        if(l1 != null) cur.next = l1;
        if(l2 != null) cur.next = l2;
        return dummy.next;
    }
}