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
        ListNode a = pHead1;
        ListNode b = pHead2;//表头
        ListNode dummy = new ListNode(0);
        ListNode tail = dummy;
        //边界
        if(pHead1 == null) return pHead2;
        if(pHead2 == null) return pHead1;

        while(a!=null && b!=null){
            if(a.val<=b.val){
                tail.next = a;
                a = a.next;
            }
            else{
                tail.next = b;
                b = b.next;
            }
            tail = tail.next;
        }
        if(a==null) tail.next = b;
        if(b==null) tail.next = a;
        return dummy.next;
    }
}