Merge Two Sorted Lists

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.

 

public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null) {
        	return l2;
        }
        if (l2 == null) {
        	return l1;
        }
        ListNode head, tail;
        if (l1.val < l2.val) {
        	head = tail = l1;
        	l1 = l1.next;
        } else {
        	head = tail = l2;
        	l2 = l2.next;
        }
        while (l1!=null && l2!=null) {
        	if (l1.val < l2.val) {
        		tail.next = l1;
        		tail = l1;
        		l1 = l1.next;
        	} else {
        		tail.next = l2;
        		tail = l2;
        		l2 = l2.next;
        	}
        }
        tail.next = (l1==null)?l2:l1;
        return head;
    }
}

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        if (l1 == NULL) {
            return l2;
        }
        if (l2 == NULL) {
            return l1;
        }
        ListNode* head;
        ListNode* tail;
        if (l1->val < l2->val) {
            head = tail = l1;
            l1 = l1->next;
        } else {
            head = tail = l2;
        	l2 = l2->next;
        }
        while (l1!=NULL && l2!=NULL) {
        	if (l1->val < l2->val) {
        		tail->next = l1;
        		tail = l1;
        		l1 = l1->next;
        	} else {
        		tail->next = l2;
        		tail = l2;
        		l2 = l2->next;
        	}
        }
        tail->next = (l1==NULL)?l2:l1;
        return head;
    }
};