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.
if... else if不要偷懒直接写 if...if...
/**
* 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 *head = NULL,*temp = head;
if(l1 == NULL && l2 == NULL)return NULL;
if(l1 == NULL && l2 != NULL)return l2;
if(l1 != NULL && l2 == NULL)return l1;
while(l1 != NULL && l2 != NULL)
{
if(l1->val <= l2->val)
{
if(head == NULL)
{
head = l1;
temp = head;
l1 = l1->next;
continue;
}
temp->next = l1;
l1 = l1->next;
temp = temp->next;
}
else if(l1->val > l2->val)
{
if(head == NULL)
{
head = l2;
temp = head;
l2 = l2->next;
continue;
}
temp->next = l2;
l2 = l2->next;
temp = temp->next;
}
}
if(l1 == NULL)temp ->next = l2;
else if(l2 == NULL)
temp ->next =l1;
return head;
}
};