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(0); // 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 -> 。