# LC 83. Remove Duplicates from Sorted List

### [Problem link](https://leetcode.com/problems/remove-duplicates-from-sorted-list/)

###### tags: `leedcode` `easy` `c++` `Linked List`

Given the <code>head</code> of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list **sorted** as well.

**Example 1:**
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/04/list1.jpg" style="width: 302px; height: 242px;" />

Input: head = [1,1,2]
Output: [1,2]

**Example 2:**
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/04/list2.jpg" style="width: 542px; height: 222px;" />

Input: head = [1,1,2,3,3]
Output: [1,2,3]

**Constraints:**

- The number of nodes in the list is in the range <code>[0, 300]</code>.
- <code>-100 <= Node.val <= 100</code>
- The list is guaranteed to be **sorted** in ascending order.

## Solution 1
#### C++

/**
 * 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) {
        if (head == nullptr) {
            return nullptr;
        }
        ListNode *cur = head;
        while (cur->next) {
            if (cur->val == cur->next->val) {
                cur->next = cur->next->next;
            } else {
                cur = cur->next;
            }
        }
        return head;
    }
};

>### Complexity
>| | Time Complexity | Space Complexity |
>| ----------- | --------------- | ---------------- |
>| Solution 1 | O(n) | O(1) |

## Note
x