Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

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/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode* deleteDuplicates(ListNode* head) { if(head == NULL || head->next == NULL){ return head; } //create a dummy node to avoid the case of head value getting repeated which is difficult to handle struct ListNode *res = new struct ListNode(0); res->next = head; struct ListNode *cur = res; while(cur->next && cur->next->next){ //if the next value is same as its next value if(cur->next->val == cur->next->next->val){ int val = cur->next->val; //move forward if same value is repeating while(cur->next && cur->next->val == val){ cur->next = cur->next->next; } }else{ cur = cur->next; } } //return next of the dummy node return res->next; } };