002_reverse_linked_list

Reverse linked list

• 🧩 Problem link: Leetcode
• 🚦 Difficulty: 🟢 Easy

💡 Approach

• Set curr->next node to be the prev one, always updating in each loop prev with curr node
• But using recursion

🕒 Time and Space Complexity

• Time: O(n)
• Space: O(n)

✅ Solution

class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if (!head) {
            return nullptr;
        }

        ListNode* newHead = head;
        if (head->next) {
            newHead = reverseList(head->next);
            head->next->next = head;
        }
        head->next = nullptr;

        return newHead;
    }
};