[leetcode]Merge Two Sorted Lists

/**

 * 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) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        if(!l1) return l2;

        if(!l2) return l1;

        

        if(l1->val < l2->val){

            l1->next = mergeTwoLists(l1->next, l2);

            return l1;

        }else{

            l2->next = mergeTwoLists(l2->next, l1);

            return l2;

        }

        

        

    }

};