leetcode-206-Reverse Linked List

Reverse a singly linked list.

Example:

Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL

Follow up:

A linked list can be reversed either iteratively or recursively. Could you implement both?

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        if(head == null || head.next == null)
            return head;
        ListNode prev = null;
        ListNode curr = head;
        prev = new ListNode(curr.val);
        curr = curr.next;
        while(curr != null)
        {
            ListNode temp = new ListNode(curr.val);
            temp.next = prev;
            prev = temp;
            curr = curr.next;
        }
        return prev;
    }
}