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 p = new ListNode(-1);
        ListNode head=p;

        while (pHead1 != null && pHead2 != null) {
            if (pHead1.val <= pHead2.val) {
                p.next = pHead1;
                pHead1 = pHead1.next;
            } else {
                p.next = pHead2;
                pHead2 = pHead2.next;
            }
            p = p.next;
        }
        if (pHead2 == null) //将剩余的链表拼在后面
            p.next = pHead1;
        if (pHead1 == null)
            p.next = pHead2;
        return head.next;
    }
}