# 83-Remove Duplicates from Sorted List
###### tags: `Easy`
## Question
https://leetcode.com/problems/remove-duplicates-from-sorted-list/
## Key
- 因為順序排序過，重複數一定相鄰，所以跟下一個比較就好
## Reference

## trivial Solution

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
       ListNode* cur = head;
        while(cur != NULL && cur->next != NULL)
        {
            if(cur->val == cur->next->val)
            {
                cur->next = cur->next->next;
            }
            else
            {
                cur = cur->next;    
            }
        }
        return head;
        
    }
};

### Recursive solution

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if(head == NULL || head->next == NULL) return head;

        head->next = deleteDuplicates(head->next);

        return head->val == head->next->val ? head->next : head;
    }
};