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
        if (pHead1 == null) {
            return pHead2;
        }
        if (pHead2 == null) {
            return pHead1;
        }
        ListNode head = new ListNode(-1);
        ListNode cur = head;
        while (pHead1 != null && pHead2 != null) {
            if (pHead1.val <= pHead2.val) {
                cur.next = pHead1;
                pHead1 = pHead1.next;
            } else {
                cur.next = pHead2;
                pHead2 = pHead2.next;
            }
            cur = cur.next;
        }
        if (pHead1 != null) {
            cur.next = pHead1;
        } else {
            cur.next = pHead2;
        }

        //根据JVM的回收机制，对于强引用对象要手动置null回收
        ListNode pHead3 = head.next;
        head = null;
        return pHead3;
    }
}