java 甲兵 - 08日至2019会话-206-反向链接列表

Posted 2021-05-07

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

        ListNode previousNode = null;
        ListNode currentNode = head;
        ListNode nextNode = null;
        while (currentNode != null) {
            nextNode = currentNode.next;
            currentNode.next = previousNode;
            previousNode = currentNode;
            currentNode = nextNode;
        }
		
        return previousNode;
    }
}

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

       return nextNode;
    }
}