数据结构--线性链式表倒数第K项

https://pintia.cn/problem-sets/910354764736491520/problems/910354975319912451（点击打开链接）

题目大意：给你一系列数，求倒数第k个数。
分析：一道思路题吧，虽然简单的数组就可以做，但学的毕竟是数据结构，还得用数组来做，一开始用的双向链表，写不出来，后来改成单向链表，卡在大数据上了。后来同学让帮忙找bug，看了人家的代码，用的是单向链表逆序创建，倒数第k个就成了正数第k个，不得不佩服啊！！！
代码：

#include <iostream>#include <algorithm>#include <string>#include <cstring>#include <cstdio>#define OK 1#define ERROR 0#define TRUE 1#define FALSE 0#define INFEASIBLE -1#define OVERFLOW -2#define ll long longusing namespace std;typedef int Status;typedef ll ElemType;//随机大数据，改成ll才能过typedef struct LNode{    ElemType data;    int length;    struct LNode *next;} LNode,*LinkList;Status Creat_L(LinkList &L);Status Print_L(LinkList &L,int k,ElemType &e);int main(){    LinkList L;    L = (LNode*)malloc(sizeof(LNode));    if(!L) exit(OVERFLOW);    int k;    scanf("%d",&k);    Creat_L(L);    ElemType res;    Print_L(L,k,res);    if(!res)        cout << "NULL" << endl;    else        cout << res << endl;}Status Creat_L(LinkList &L){    LNode *curPtr,*rearPtr;    rearPtr = L;    L -> length = 0;    while(1)    {        curPtr = (LNode*)malloc(sizeof(LNode));        if(!curPtr) exit(OVERFLOW);        //原先用的int类型的，后来改成ll，但是这里忘改了，结果wa了一晚上。。。。。。        scanf("%lld",&curPtr -> data);        if((curPtr -> data) < 0)        {            rearPtr -> next = NULL;            return OK;        }        else        {            curPtr -> next = NULL;            rearPtr -> next = curPtr;            rearPtr = curPtr;            L -> length++;        }    }}Status Print_L(LinkList &L,int k,ElemType &e){    if(k <= 0 || k > L -> length)        return ERROR;    int ans = 1;    LNode *curPtr;    curPtr = L -> next;    while(ans < L -> length - k + 1)    {        curPtr = curPtr -> next;        ans++;    }    e = curPtr -> data;    return OK;}

• 用的单链表，输出倒数第k个，也就是输出正数第length - k + 1个，思路还不是自己想出来的。。。。。

和上面的思路差不多，但是这个给人一种更高大上的感觉，链表逆序创建。
代码：

#include<stdio.h>#include<malloc.h>#include<stdlib.h>//函数状态码定义#define TRUE        1#define FALSE       0#define OK          1#define ERROR       0#define INFEASIBLE -1#define OVERFLOW   -2typedef int  Status;typedef int ElemType;typedef struct LNode{    ElemType data;    struct LNode *next;    int length;} LNode,*LinkList;Status Creat_L(LinkList &L);Status Print_L(LinkList &L,int k);int main(){    LinkList L;    int k;    scanf("%d",&k);    Creat_L(L);    Print_L(L,k);}Status Creat_L(LinkList &L){    L = (LNode*)malloc(sizeof (LNode));    if(!L)  exit(OVERFLOW);    LNode *curPtr,*rearPtr;    rearPtr = L;    L -> next = NULL;    L -> length = 0;    int m;    while(scanf("%d",&m) && m >= 0)    {        curPtr = (LNode*)malloc(sizeof (LNode));        if(!curPtr)  exit(OVERFLOW);        //链表逆序创建        curPtr -> data = m;        curPtr -> next = L -> next;        L -> next = curPtr;        L -> length++;    }    return OK;}Status Print_L(LinkList &L,int k){    if(k <= 0 || k > L -> length)    {        printf("NULL\n");        return ERROR;    }    else    {        LNode *curPtr;        curPtr = L -> next;        int ans = 1;        while(ans < k)        {            curPtr = curPtr -> next;            ans++;        }        printf("%d\n",curPtr -> data);        return OK;    }}

真的有必要和别人的代码进行比对啊！！！

双向链表也搞定了，嗯，真的要静下心来才可以，不然效率会更低的！！！！

代码：

#include <iostream>#include <algorithm>#include <cstdio>#include <cstring>#include <string>#define OK 1#define TRUE 1#define FALSE 0#define ERROR 0#define INFEASIBLE -1#define OVERFLOW -2using namespace std;typedef int Status;typedef int ElemType;typedef struct LNode{    ElemType data;    int length;    struct LNode *prior,*next;}LNode,*LinkList;Status Creat_L(LinkList &L);Status Print_L(LinkList &L,int k);int main(){    LinkList L;    L = (LNode*)malloc(sizeof(LNode));    if(!L)  exit(OVERFLOW);    int k;    scanf("%d",&k);    L -> next = NULL;    L -> prior = NULL;    Creat_L(L);    Print_L(L,k);}Status Creat_L(LinkList &L){    LNode *curPtr,*rearPtr;    rearPtr = L;    L -> length = 0;    int m;    while(scanf("%d",&m) && m >= 0)    {        curPtr = (LNode*)malloc(sizeof(LNode));        if(!curPtr)            exit(OVERFLOW);        curPtr -> data = m;        curPtr -> prior = rearPtr;        curPtr -> next = NULL;        rearPtr -> next = curPtr;        rearPtr = curPtr;        L -> length++;    }    rearPtr -> next = L;    L -> prior = rearPtr;    return OK;}Status Print_L(LinkList &L,int k){    if(k <= 0 || k > L -> length)    {        printf("NULL\n");        return OK;    }    int ans = 1;    LNode *curPtr;    curPtr = L -> prior;    while(ans < k)    {        curPtr = curPtr -> prior;        ans++;    }    printf("%d\n",curPtr -> data);    return OK;}