倒数第k个点

ListNode* FindKthToTail(ListNode* pListHead, unsigned int k)
{
    if(pListHead == nullptr || k == 0)
        return nullptr;

    ListNode *pAhead = pListHead;
    ListNode *pBehind = nullptr;

    for(unsigned int i = 0; i < k - 1; ++ i)
    {
        if(pAhead->m_pNext != nullptr)
            pAhead = pAhead->m_pNext;
        else
        {
            return nullptr;
        }
    }

    pBehind = pListHead;
    while(pAhead->m_pNext != nullptr)
    {
        pAhead = pAhead->m_pNext;
        pBehind = pBehind->m_pNext;
    }

    return pBehind;
}