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。
示例:
输入:1->2->4, 1->3->4 输出:1->1->2->3->4->4
这个题就很简单了吧,直接递归:
/**
* 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 && l2 == NULL)
return NULL;
if(l1 == NULL && l2 != NULL)
return l2;
if(l1 != NULL && l2 == NULL)
return l1;
ListNode* afterMergeHead;;
if(l1->val <= l2->val)
{
afterMergeHead = l1;
l1 = l1->next;
afterMergeHead->next = mergeTwoLists(l1, l2);
}
else
{
afterMergeHead = l2;
l2 = l2->next;
afterMergeHead->next = mergeTwoLists(l1, l2);
}
return afterMergeHead;
}
};