[LeetCode] 21 Merge Two Sorted Lists 合并两个有序链表

[LeetCode]21 Merge Two Sorted Lists 合并两个有序链表

Description

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

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

题意

将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。

题解

新构建一个链表，然后有序插入即可，注意，当一个链表为空时，直接将另一个链表插在后面即可。

代码

/**
 * 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* pRoot=new ListNode(-1);
        ListNode* pTail;
        pTail = pRoot;
        while(l1!=NULL&&l2!=NULL){
            if(l1->val<l2->val){
                pTail->next = l1;
                l1 = l1->next;
            }else{
                pTail->next = l2;
                l2 = l2->next;
            }
            pTail = pTail->next;
        }
        pTail->next = l1 ? l1 : l2;
        return pRoot->next;
    }
};

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