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
Solution in C++
/**
* 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 *h=NULL, *p, *c;
while(l1 || l2) {
if (!l1) { c=l2; l2=l2->next; }
else if (!l2) { c=l1; l1=l1->next; }
else if (l1->val<l2->val) { c=l1; l1=l1->next; }
else { c=l2; l2=l2->next; }
if (!h) {
h=new ListNode(c->val);
p=h;
}
else {
p->next = new ListNode(c->val);
p=p->next;
}
}
return h;
}
};