剑指offer面试题15：链表中倒数第k个结点

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题目：输入一个链表，输出该链表中倒数第K个结点。链表的尾结点是倒数第1个节点。
思路：两个指针相差k-1。

#include <iostream>using namespace std;struct ListNode {  int m_nValue;  ListNode *m_pNext;};ListNode *CreateList() {  int a;  cin >> a;  ListNode *head;  head = NULL;  if (a != -1) {    head = new ListNode;    head->m_nValue = a;    head->m_pNext = CreateList();  }  return head;}ListNode *FindKthToTail(ListNode *phead, int k) {  if (phead == NULL || k == 0) {    cout << "Invalid Input!" << endl;    return NULL;  }  ListNode *pFirst = phead;  ListNode *pSecond = phead;  for (int i = 1; i < k; i++) {    if (pFirst->m_pNext != NULL)      pFirst = pFirst->m_pNext;    else {      cout << "Invalid k!" << endl;      return NULL;    }  }  while (pFirst->m_pNext != NULL) {    pFirst = pFirst->m_pNext;    pSecond = pSecond->m_pNext;  }  cout << pSecond->m_nValue << endl;  return pSecond;}int main() {  int k = 1;  ListNode *head = CreateList();  ListNode *Kth = FindKthToTail(head, k);  (Kth == NULL) ? cout << "Invalid!" << endl : cout << Kth->m_nValue << endl;  return 0;}

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