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
        if(pHead1==null){
            return pHead2;
        }else if(pHead2==null){
            return pHead1;
        }
        ListNode du = new ListNode(-1);
        if(pHead1.val<pHead2.val){
            du.next = pHead1;
            pHead1 = pHead1.next;
        }else {
            du.next = pHead2;
            pHead2 = pHead2.next;
        }
        ListNode start = du.next;
       while (pHead1!=null||pHead2!=null){
           ListNode tem = start.next;
           if(pHead1!=null&&pHead2!=null)
           if(pHead1.val<pHead2.val){
               start.next = pHead1;
               pHead1 = pHead1.next;
               start = start.next;
           }else {
               start.next = pHead2;
               pHead2 = pHead2.next;
               start = start.next;
           }
           else if(pHead1==null){
               start.next = pHead2;
               pHead2 = pHead2.next;
               start = start.next;
           }
           else {
               start.next = pHead1;
               pHead1 = pHead1.next;
               start = start.next;
           }
       }

        return  du.next;
    }
}