203. Remove Linked List Elements| Leetcode solution

 203. Remove Linked List Elements

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

 

Example 1:

Input: head = [1,2,6,3,4,5,6], val = 6
Output: [1,2,3,4,5]

Example 2:

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

Example 3:

Input: head = [7,7,7,7], val = 7
Output: []

 

Constraints:

• The number of nodes in the list is in the range [0, 104].
• 1 <= Node.val <= 50
• 0 <= val <= 50

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* removeElements(ListNode* head, int val) {

        

        

        

        if(head == NULL)

            return head;

        

        

        ListNode* temp = head;

        while(  temp->next != NULL )

        {   

            

            if(temp ->next->val == val  )

                temp ->next = temp->next->next;

            else

            temp = temp->next;

        }

        if(head->val == val)

        {    

            if(head->next == NULL)

            {

                return NULL;

            }

            else

            {

                head = head->next;

            }

      

        }

        return head;

        

    }

};