链表的巧解

#ifndef COUNT_BACKWARD_H
#define COUNT_BACKWARD_H
#include<iostream>
struct  ListNode
{
	int m_value; 
	struct ListNode *m_pNext; 
};
ListNode *findBackward_k(ListNode **head,int k_backward){
	if(head==NULL||*head==NULL||k_backward==0){
		return NULL ; 
	}
	if((*head)->m_pNext==NULL&&k_backward==1){
		return *head; 
	}
	ListNode *m_phead=*head; 
	ListNode *pre_kbackward=m_phead; 
	ListNode *m_pend=m_phead-1; 
	int		  count_dis=k_backward; 
	while(m_pend->m_pNext!=NULL){
		if(count_dis>0){
			m_pend=m_pend->m_pNext; 
			count_dis--; 
			continue; 
		}
		pre_kbackward=pre_kbackward->m_pNext; 
		m_pend=m_pend->m_pNext;
	}
	if(count_dis!=0){
		throw("invalid input value"); 
	}
	return pre_kbackward; 
}
#endif