T4

#include <vector>
#include <iostream>
#include <string>
#include <c++/algorithm>
#include <c++/map>
using namespace std;
struct ListNode {
    int val;
    ListNode *next;

    ListNode(int k) : val(k), next(NULL) {

    }
};

ListNode* FindKthFromTail(ListNode* pListHead,int k) {
    if (pListHead == NULL || k == 0)//防止空的链表  和 k值 等于 0 的情况
    {
        return NULL;
    }
    ListNode *pAhead = pListHead;
    ListNode *pBehind = NULL;
    for (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;
}
int main(){
    ListNode * head = new ListNode(0);
    ListNode * p1=new ListNode(1);
    ListNode * p2=new ListNode(2);
    ListNode * p3=new ListNode(3);
    ListNode * p4=new ListNode(4);
    ListNode * p5=new ListNode(5);
    head->next=p1;
    p1->next=p2;
    p2->next=p3;
    p3->next=p4;
    p4->next=p5;
    p5->next=NULL;
    ListNode *pNode = FindKthFromTail(head, 3);
    cout<<pNode->val<<endl;
    return 0;
}