LC 21. Merge Two Sorted Lists

题目描述

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

参考答案

 /**
  * Definition for singly-linked list.
  * struct ListNode {
  *     int val;
  *     ListNode *next;
  *     ListNode(int x) : val(x), next(NULL) {}
  * };
  */
 class Solution {
 public:
     ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
         ListNode res(); // content
         ListNode* cur = &res; // pointer cur = taking addree of res
         // *content. &pointer->

         while(l1&&l2){
             if(l1->val > l2 ->val){
                 cur->next = l2;
                 l2 = l2->next;
             }else{
                 cur->next = l1;
                 l1 = l1->next;
             }
             cur = cur->next;
         }
         cur->next = l2?l2:l1;
         return res.next;
     }
 };

答案解析

新建一个空节点，不是地址，而是内容，然后将该内容对应的地址，附给一个cur指针。

进行loop

返回的时候，因为对于struct而言，提取成员时，内容使用 点，指针使用 -> 。