题解 | #链表中倒数最后k个结点#

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pHead ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    public ListNode FindKthToTail (ListNode pHead, int k) {
        // write code here
        if(pHead == null){
            return null;
        }
//         int count = 0;
//         ListNode currentNode = pHead;
//         while(currentNode != null){
//             currentNode = currentNode.next;
//             count ++;
//         }
//         if(count < k){
//             return null;
//         }
//         int offset = count - k;
//         currentNode = pHead;
//         while(offset >0){
//             currentNode = currentNode.next;
//             offset -- ;
//         }
//         return currentNode;
        if(k == 0){
            return null;
        }
        ListNode fastNode = pHead;
        for(int i = 0;i < k-1;i++){
            fastNode = fastNode.next;
            if(fastNode == null){
                return null;
            }
        }
        ListNode slow = pHead;
        while(fastNode.next != null){
            slow = slow.next;
            fastNode = fastNode.next;
        }
        return slow;
    }
}