问题:
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.
分析:
注意 p==nullptr 和 !p的不同;
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==nullptr) return l2;
if(l2==nullptr) return l1;
ListNode dummy(-1);
ListNode* p=&dummy;
while(l1!=nullptr&&l2!=nullptr){
if(l1->val>l2->val){
p->next=l2;
l2=l2->next;
}else{
p->next=l1;
l1=l1->next;
}
p=p->next;
}
p->next=l1==nullptr?l2:l1;
return dummy.next;
}
};