206. Reverse Linked List - Easy

前往題目

想法

• 之前做過，忘了要用一個prev存上一個node

思路

1. 疊代所有node
2. 每個node都紀錄一下前一個，然後切換當前的node

Code

class Solution {
    public ListNode reverseList(ListNode head) {
        if (head == null || head.next == null) return head;

        ListNode prev = null, curr = head;

        while (curr != null) {
            ListNode tempNode = curr.next;
            curr.next = prev;
            prev = curr;
            curr = tempNode;
        }
        return prev;
    }
}