反转链表,基本操作
Example:
Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL
public ListNode reverseList(ListNode head) {
/* iterative solution */
ListNode newHead = null;
while (head != null) {
ListNode next = head.next;
head.next = newHead;
newHead = head;
head = next;
}
return newHead;
}