206. Reverse Linked List

Reverse a singly linked list.

public class Solution {
    public ListNode reverseList(ListNode head) {
        if (head == null || head.next == null){
            return head;
        }
        
        ListNode pre = null;
        ListNode cur = head;
        
        while(cur != null){
            ListNode next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }
        return pre;
        
    }
}