LeetCode 21. 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.

没什么好说的，把两个排好序的链表合成一个就行了

/**
 * 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)return l2;
        if (!l2)return l1;
        ListNode *head,*current;
        if (l1->val < l2->val)
        {
            head = l1;
            l1 = l1->next;
        }
        else
        {
            head = l2;
            l2 = l2->next;
        }
        current = head;
        while (l1&&l2)
        {
            if (l1->val < l2->val)
            {
                current->next = l1;
                l1 = l1->next;
            }
            else
            {
                current->next = l2;
                l2 = l2->next;
            }
            current = current->next;
        }
        if (l1)
        {
            current->next = l1;
        }
        else current->next = l2;
        return head;
    }
};