203. Remove Linked List Elements

📝 Problem Details

• Title: 203. Remove Linked List Elements
• Link: https://leetcode.com/problems/remove-linked-list-elements/
• Difficulty: Easy
• Tags/Categories: Linked-List

💭What Were My Initial Thoughts?

similar to implemented solution with some missing logic 

🤔What Did I Struggle With?

forgot to delete / free up memory for removed nodes

💡 Explanation of Solution

- create a dummy node and initialize its values to 0, point its next to head
- create another list node curr that is equal to the dummy node

- traverse the list while curr->next is not null
	- if curr->next is equal to val
		- create a temp node that is equal to curr->next
		- make curr->next equal to curr->next->next
		- delete temp
	- else move to the next node 

- get rid of the dummy node by creating a newHead node equal to dummy->next
- delete dummy
- return the newHead

⌛ Complexity Analysis

Time Complexity: O(n)
Space Complexity: O(1)

💻 Implementation of Solution

class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
    
        ListNode* dummy = new ListNode(0, head);
        ListNode* curr = dummy;
        
        while(curr->next != nullptr) {
            if(curr->next->val == val) {
                ListNode* temp = curr->next;
                curr->next = curr->next->next;
                delete temp;
            } else {
                curr = curr->next;
            }
        }
  
        ListNode* newHead = dummy->next;
        delete dummy;
        return newHead;
    }
};