Problem Statement

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.

Example 1:

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

Example 2:

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

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.

Problem Link

Remove Duplicates from Sorted List - LeetCode

Code

/**
 * 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 *p1 = head;
        
        while(p1)
        {
            while(p1->next&&p1->val!=p1->next->val)
                p1 = p1->next;
            
            ListNode *p2 = p1->next;
            
            if(!p2)
                return head;
            
            while(p2->next&&p2->val==p2->next->val)
                p2 = p2->next;
            
            p1->next = p2->next;
        }
        
        return head;
       
        
        
    }
};