LeetCode/206.cpp at master · nitin-maharana/LeetCode · GitHub

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/*
 * Written by Nitin Kumar Maharana
 * nitin.maharana@gmail.com
 */

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */

//Iterative Solution.
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        ListNode *prev, *curr, *next;

        prev = next = nullptr;

        curr = head;

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

        return prev;
    }
};

//Recursive Solution.
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if(!head || !head->next)
            return head;

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