18. Reverse a Doubly Linked List

The problem can be found at the following link: Question Link

My Approach

To reverse a doubly linked list, I go through the list, swapping the prev and next pointers for each node while updating the head during each iteration.

Time and Auxiliary Space Complexity

• Time Complexity: O(N), where N is the number of nodes in the doubly linked list.

• Auxiliary Space Complexity: O(1), as the reversal is done in-place without using additional space.

Code (C++)

class Solution {
public:
    Node* reverseDLL(Node* head) {
        Node* curr = head;

        while (curr) {
            head = curr;
            Node* prev = curr->prev;
            curr->prev = curr->next;
            curr->next = prev;
            curr = curr->prev;
        }

        return head;
    }
};

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