LeetCode 21. Merge Two Sorted Lists(链表题目)
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
思路分析
该题目比较简单,建立一个虚拟头结点,然后穿针引线(改变节点指针指向)即可,和归并排序中一样,注意判空,以及最后把退出循环没有遍历完的链表接上即可。
具体代码:
/**
* 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) {
if(l1==NULL)
return l2;
if(l2==NULL)
return l1;
//利用一个虚拟头结点,后边就是改变指针的指向就可以
ListNode* dummy=new ListNode(0);
ListNode* p=dummy;
while(l1&&l2)
{
if(l1->val<l2->val)
{
p->next=l1;
l1=l1->next;
}
else
{
p->next=l2;
l2=l2->next;
}
p=p->next;
}
if(l1)
p->next=l1;
if(l2)
p->next=l2;
return dummy->next;
}
};