题解 | #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 pHead1, ListNode pHead2) {
        // write code here
        // write code here
        ListNode head = null;
        ListNode pre = null;

        while (pHead1 != null || pHead2 != null) {
            ListNode newNode = null;
            if (pHead1 != null && pHead2 != null) {
                if (pHead1.val <= pHead2.val) {
                    newNode = new ListNode(pHead1.val);
                    pHead1 = pHead1.next;
                } else {
                    newNode = new ListNode(pHead2.val);
                    pHead2 = pHead2.next;
                }
            } else if (pHead1 != null && pHead2 == null) {
                newNode = new ListNode(pHead1.val);
                pHead1 = pHead1.next;
            } else if (pHead1 == null && pHead2 != null) {
                newNode = new ListNode(pHead2.val);
                pHead2 = pHead2.next;
            }

            if (head == null) {
                head = newNode;
                pre = head;
            } else {
                pre.next = newNode;
                pre = newNode;
            }

        }

        return head;
    }
}

比较纯粹的传递引用。