题目：
输入一个链表，输出该链表中倒数第k个节点
提示
可以用2个下标，第一个节点A先移动k-1个下标，此时2个节点A、B同时向尾节点移动，当A到达尾节点时，B则是该链表的倒数第k个节点
public class FindKTotail { public static class ListNode { ListNode next = null; int data; public ListNode(int data) { this.data = data; } } public static void main(String args[]) { ListNode node1 = new ListNode(1); ListNode node2 = new ListNode(2); ListNode node3 = new ListNode(3); ListNode node4 = new ListNode(4); ListNode node5 = null; node1.next = node2; node2.next = node3; node3.next = node4; node4.next = node5; printLinkedList(node1); int data; ListNode kToTail = findKToTail(0, node1); if (kToTail != null) { data = kToTail.data; System.out.print(data); } else { System.out.println("can not find k"); } } private static ListNode findKToTail(int k, ListNode head) { if (head == null || k == 0) { // 边界值 return null; } ListNode pAhead = head; ListNode pBhead = head; for (int i = 0; i < k - 1; i++) { if (pAhead.next != null) { // 边界值 pAhead = pAhead.next; } else { return null; // 边界值 } } while (pAhead.next != null) { pBhead = pBhead.next; pAhead = pAhead.next; } return pBhead; } private static void printLinkedList(ListNode head) { if (head != null) { System.out.print(head.data + "->"); } while (head.next != null) { head = head.next; System.out.print(head.data + "->"); } System.out.println(); } }GitHub地址
