[LeetCode] Grind 75 questions (18/75) Reverse Linked List

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode prev = null;
        
        while(head != null) {
            ListNode next = head.next;
            head.next = prev;
            prev = head;
            head = next;
        }

        return prev;
    }
}