【c语言】单链表的基础面试题

1.比较顺序表和链表的优缺点，说说它们分别在什么场景下使用？
答：
1，顺序表支持随机访问，单链表不支持随机访问。
2，顺序表插入/删除数据效率低，时间复杂度是O(n)，（除尾插，尾删）；单链表插入/删除效率高，时间复杂度是O(1)。
3，顺序表的CPU高速缓存效率更高，单链表的低。
在插入和删除频繁的程序中适合用链表
2.从尾到头打印单链表
3.删除一个无头单链表的非尾节点
4.在无头单链表的一个节点前插入一个节点
5.单链表实现约瑟夫环
6.逆置/反转单链表
7.单链表排序（冒泡排序&快速排序）
8.合并两个有序链表,合并后依然有序
9.查找单链表的中间节点，要求只能遍历一次链表
10.查找单链表的倒数第k个节点，要求只能遍历一次链表

代码如下：

#pragma once#include<stdio.h>#include<malloc.h>#include<assert.h>typedef int DataType;typedef struct ListNode{    DataType data;    struct ListNode* next;}ListNode;//创建一个结点ListNode* BuyNode(DataType x){    ListNode* node = (ListNode*)malloc(sizeof(ListNode));    node->data = x;    node->next = NULL;    return node;}//尾插void PushBack(ListNode** pplist, DataType x){    if (*pplist == NULL)    {        *pplist = BuyNode(x);    }    else    {        ListNode* tail = *pplist;        while (tail->next)        {            tail = tail->next;        }        tail->next = BuyNode(x);    }}//查找一个结点ListNode* FindList(ListNode* plist, DataType x){    ListNode* cur = plist;    while (cur)    {        if (cur->data == x)        {            return cur;        }        else        {            cur = cur->next;        }    }    return NULL;}//从尾到头打印单链表-----(递归法)void PrintListFromTailtoHead(ListNode* plist){    ListNode* cur = plist;    if (cur != NULL)    {        PrintListFromTailtoHead(cur->next);        printf("%d->", cur->data);    }}//删除无头单链表的非尾结点--（把pos->next结点的data给pos的data,然后删除pos->next结点）void EraseNonTail(ListNode* pos){    assert(pos&&pos->next);    ListNode* next = pos->next;    pos->data = next->data;    pos->next = next->next;//摘结点    free(next);}//在无头单链表的一个结点前插入一个结点void InsertNonTeal(ListNode *pos, DataType x){    assert(pos);    ListNode* newnode = BuyNode(x);    ListNode* next = pos->next;    pos->next = newnode;    newnode->next = next;    newnode->data = pos->data;    pos->data = x;}//单链表实现约瑟夫环ListNode* JosepRing(ListNode* list, int k)//删除第K个结点，把这个结点的data改成下一个结点的data，然后删除第K个结点的下一个结点。{    if (!list)    {        return NULL;    }    ListNode* cur = list;    while (cur->next != cur)    {        int count = k;        while (--count)        {            cur = cur->next;        }        ListNode* next = cur->next;        cur->data = next->data;        free(next);    }    return cur;}//翻转/逆置单链表ListNode* Reverse(ListNode* list){    ListNode* newlist = NULL;    ListNode* cur = list;    while (cur)    {        //摘结点        ListNode* tmp = cur;        cur = cur->next;        //插结点--（既在newlist前插入tmp）        tmp->next = newlist;        newlist = tmp;    }    return newlist;}//链表排序（冒泡）void BubbleSort(ListNode* list){    if (list == NULL&&list->next != NULL)    {        return;    }    ListNode* tail = NULL;    while (tail != list->next)    {        ListNode* prev = list;        ListNode* next = prev->next;        while (next != tail)        {            if (prev->data > next->data)//交换两个结点的值，大的放在后            {                DataType tmp = next->data;                next->data = prev->data;                prev->data = tmp;            }            prev = prev->next;            next = next->next;        }        tail = prev;    }}//合并两个有序链表，合并后依然有序ListNode* Merge(ListNode* list1, ListNode* list2){    if (!list1)    {        return list2;    }    if (!list2)    {        return list1;    }    //先找出两个链表中小的一个结点，把它摘下来做新链表的头结点    ListNode* list = NULL;    if (list1->data < list2->data)    {        list = list1;        list1 = list1->next;    }    else    {        list = list2;        list2 = list2->next;    }    //然后开始尾插    ListNode* tail = list;    while (list1&&list2)    {        if (list1->data < list2->data)        {            tail->next = list1;            list1 = list1->next;        }        else        {            tail->next = list2;            list2 = list2->next;        }        tail = tail->next;    }    if (!list1)    {        tail->next = list2;    }    if (!list2)    {        tail->next = list1;    }    return list;}//查找链表的中间结点，要求只能遍历一次链表--(快慢指针法)ListNode* FindMidNode(ListNode* list){    if (!list)    {        return NULL;    }    ListNode* slow = list;    ListNode* fast = list;    while (fast&&fast->next)    {        slow = slow->next;        fast = fast->next->next;    }    return slow;}//查找链表倒数第K个结点，要求只能遍历一次链表----（快慢指针法）ListNode* FindTail_k_Node(ListNode* list,int K){    ListNode* slow = list;    ListNode* fast = list;    while (--K)    {        if (fast == NULL)//fast为空说明K值大于链表长度。既K值无效        {            return NULL;        }        fast = fast->next;    }    while (fast->next)    {        slow = slow->next;        fast = fast->next;    }    return slow;}//打印链表void PrintList(ListNode* plist){    if (!plist)    {        printf("->NULL\n");        return;    }    else    {        ListNode* cur = plist;        while (cur)        {            printf("%d->", cur->data);            cur = cur->next;        }        printf("NULL\n");        return;    }    /*ListNode* cur = plist;    while (cur)    {        printf("%d->", cur->data);        cur = cur->next;    }    printf("NULL\n");    return;*/}

测试代码：

void TestList1(){    ListNode* list = NULL;    PushBack(&list, 1);    PushBack(&list, 2);    PushBack(&list, 3);    PushBack(&list, 4);    PrintList(list);    PrintListFromTailtoHead(list);}void TestList2(){    ListNode* list = NULL;    PushBack(&list, 1);    PushBack(&list, 2);    PushBack(&list, 3);    PushBack(&list, 4);    PrintList(list);    ListNode* pos = FindList(list, 3);    EraseNonTail(pos);    PrintList(list);}void TestList3(){    ListNode* list = NULL;    PushBack(&list, 1);    PushBack(&list, 2);    PushBack(&list, 3);    PushBack(&list, 5);    PrintList(list);    ListNode* pos = FindList(list, 1);    InsertNonTeal(pos, 4);    PrintList(list);}void TestList4(){    ListNode* list = NULL;    PushBack(&list, 1);    PushBack(&list, 2);    PushBack(&list, 3);    PushBack(&list, 4);    PushBack(&list, 5);    ListNode* reverselist = Reverse(list);    PrintList(reverselist);}void TestList5(){    ListNode* list = NULL;    PushBack(&list, 8);    PushBack(&list, 2);    PushBack(&list, 1);    PushBack(&list, 3);    PushBack(&list, 6);    PrintList(list);    BubbleSort(list);    PrintList(list);}void TestList6(){    ListNode* list1 = NULL;    PushBack(&list1, 1);    PushBack(&list1, 3);    PushBack(&list1, 5);    PushBack(&list1, 7);    PushBack(&list1, 6);    PrintList(list1);    ListNode* list2 = NULL;    PushBack(&list2, 2);    PushBack(&list2, 4);    PushBack(&list2, 6);    PushBack(&list2, 8);    PushBack(&list2, 9);    PrintList(list2);    ListNode* list = Merge(list1, list2);    PrintList(list);    ListNode* mid = FindMidNode(list);    printf("%d\n", mid->data);}void TestList7(){    ListNode* list1 = NULL;    PushBack(&list1, 1);    PushBack(&list1, 3);    PushBack(&list1, 5);    PushBack(&list1, 7);    PushBack(&list1, 6);    PrintList(list1);    ListNode* list = FindTail_k_Node(list1, 3);    printf("%d\n",list->data);}

主函数：

#define _CRT_SECURE_NO_WARNINGS 1#include<stdlib.h>#include"Llist.h"int main(){    //TestList();    //TestList2();    //TestList3();    //TestList4();    //TestList6();    TestList7();    system("pause");    return 0;}