private static ListNode reverse(ListNode head) {
ListNode next = null;
ListNode previous = null;
ListNode newHead = null;
ListNode current = head;
while (current != null) {
next = current.next;
if (next == null) {
newHead = current;
}
current.next = previous;
previous = current;
current = next;
}
return newHead;
}
public static ListNode reverseByRecursion(ListNode head) {
if (head == null || head.next == null)
return head;
ListNode prev = reverseByRecursion(head.next);// 把头节点之后的节点反转后，再把头节点反转即可
head.next.next = head;
head.next = null;
return prev;
}
