19. Remove Nth Node From End of List

📝 Problem Details

• Title: 19. Remove Nth Node From End of List
• Link: https://leetcode.com/problems/remove-nth-node-from-end-of-list/
• Difficulty: Medium
• Tags/Categories: Linked-List

💭What Were My Initial Thoughts?

- we will require two interations 
	- 1 to determine size of list 
	- 2nd to iterate to nth last position and remove the element

🤔What Did I Struggle With?

- dummy and temp node usage to correctly remove the node and have the previous node point to the correct next node 

💡 Explanation of Solution

same as intuition

⌛ Complexity Analysis

Time Complexity: O(n)

Space Complexity: O(1)

💻 Implementation of 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* removeNthFromEnd(ListNode* head, int n) {
        ListNode* temp = head;
 
        int size = 0;
 
        while(temp != nullptr){
            temp = temp->next;
            size++;
        }
 
        if(size - n == 0){
            head = head->next;
            return head;
        }
 
        ListNode* pre = head;
        temp=head;
 
        for(int i=0; i<size-n; i++){
            pre=temp;
            temp = temp->next;
        }
 
        pre->next=temp->next;
        return head;
    }
};