Problem:
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.
Solution:
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
ListNode *head = new ListNode(0);
ListNode *it = head;
while (l1 && l2) {
if (l1->val < l2->val)
{
it->next = l1;
l1 = l1->next;
}
else
{
it->next = l2;
l2 = l2->next;
}
it = it->next;
}
if (l1) it->next = l1;
if (l2) it->next = l2;
return head->next;
}
};
Recursive Solution:
ListNode *mergeTwoLists(ListNode *l1, ListNode *l2)
{
if (l1 == NULL) return l2;
if (l2 == NULL) return l1;
ListNode *ret = NULL;
if (l1->val < l2->val)
{
ret = l1;
ret->next = mergeTwoLists(l1->next, l2);
}
else
{
ret = l2;
ret->next = mergeTwoLists(l1, l2->next);
}
return ret;
}
