面试15：链表中倒数第K个结点

思路：两个指针一前一后，相差k-1，当后指针到达最后一个结点时，前一指针正好指向是所求结点

ListNode *FindKthToTail(ListNode* pListHead,unsigned int k){if(pListHead==NULL||k==0)return NULL;ListNode *pAhead=pListHead;ListNode *pBehind=NULL;for(unsigned int i=0;i<k-1;++i){if(pAhead->next!=NULL)pAhead=pAhead->next;else{return NULL;}pBehind=pListHead;while(pAhead->next!=NULL){pAhead=pAhead->next;pBehind=pBehind->next;}return pBehind;}