合并两个有序链表

 

迭代法：建立哨兵节点，向哨兵节点后链接

 

using System;
using System.Collections.Generic;

/*
public class ListNode
{
    public int val;
    public ListNode next;

    public ListNode (int x)
    {
        val = x;
    }
}
*/

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 vhead = new ListNode(-1);
        ListNode curr = vhead;

        while(pHead1!=null && pHead2!=null){
            if(pHead1.val<pHead2.val){
                curr.next = pHead1;
                pHead1 = pHead1.next;
                curr = curr.next;
            }
            else{
                curr.next = pHead2;
                pHead2 = pHead2.next;
                curr = curr.next;
            }
        }
        if(pHead1!=null){
            curr.next = pHead1;
        }
        else if(pHead2!=null){
            curr.next = pHead2;
        }

        return vhead.next;


    }
}