链表中倒数第k个结点

题目描述

输入一个链表，输出该链表中倒数第k个结点。

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
            val(x), next(NULL) {
    }
};*/
class Solution {
public:
    ListNode* FindKthToTail(ListNode* pListHead, unsigned int k) {
        if(!pListHead || k <=0 || k > GetLength(pListHead))
            return NULL;
        
        ListNode *pSlow = pListHead;
        ListNode *pFast = pListHead;
        
        for(int i = 0;i < k-1;i++){
            pFast = pFast->next;
        }

        while(pFast->next){
            pFast = pFast->next;
            pSlow = pSlow->next;
        }
        
        return pSlow;
    }
    
    int GetLength(ListNode *pListHead){
        int len = 0;
        ListNode *pBegin = pListHead;
        
        while(pBegin){
            len++;
            pBegin=pBegin->next;
        }
        
        return len;
    }
};