剑指 Offer - 14：链表中倒数第k个结点

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题目描述

输入一个链表，输出该链表中倒数第k个结点

题目链接：https://www.nowcoder.com/practice/529d3ae5a407492994ad2a246518148a

public class Solution {
    public ListNode FindKthToTail(ListNode head,int k) {
        if (head == null) return head;
        ListNode first = head;
        ListNode sec = head;
        for (int i = 0; i < k; i++) {
            sec = sec.next;
            if (sec == null && i != (k-1)) return null;
        }
        // 要的是正数第一个
        if (sec == null) return head;
        // 否则
        while (sec != null) {
            first = first.next;
            sec = sec.next;
        }
        return first;
    }
}