# (Easy) 21. Merge Two Sorted Lists
## Run Code

## 題意
合併兩個List
## 解題思路
就合併兩個List啊
## 困難之處
我懷念寫cpp檔，搞懂他的function花了我好多時間，我好爛==
## Code

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}  i have no idea
 *     ListNode(int x) : val(x), next(nullptr) {} i have no idea
 *     ListNode(int x, ListNode *next) : val(x), next(next) {} i have no idea
 * };
 */
class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        if(l1==NULL) return l2;
        if(l2==NULL) return l1;
        
        if(l2->val <= l1->val){
            l2->next = mergeTwoLists(l1, l2->next);
            return l2;
        }
        else{
            l1->next = mergeTwoLists(l1->next, l2);
            return l1;
        }
    }
};

###### tags: `leetcode`