Problem

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

Constraints:

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

Example1

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

Example2

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

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) {
        if(!head || !head->next)
            return head;
        
        ListNode *cur = head;
        while(cur)
        {
            ListNode *next = cur->next;
            while(next && next->val == cur->val)
                next = next->next;
            cur->next = next;
            cur = cur->next;
        }

        return head;

    }
};