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 after1 = pHead1.next;
        // ListNode after2 = pHead2.next;

        ListNode dummy = new ListNode(-10000);
        ListNode pos = dummy;
        while(pHead1 != null && pHead2 != null) {
            if(pHead1.val < pHead2.val) {
                pos.next = pHead1;
                pos = pos.next;
                pHead1 = pHead1.next;    
            } else {
                pos.next = pHead2;
                pos = pos.next;
                pHead2 = pHead2.next;
            }
        }
        if(pHead1 == null) {
            pos.next = pHead2;
        } else {
            pos.next = pHead1;
        }

        return dummy.next;
    }
}