一、简介

手写链表实现以下功能

1. 尾插
2. 获取指定下标的元素
3. 按照指定位置插入元素
4. 打印链表内容
5. 删除指定元素
6. 释放整个链表
7. 链表反转
8. 链表中相邻元素的和最大的两个元素的第一个节点，且返回和的最大值

二、源代码

LinkedList.h

#ifndef _LINKEDLIST_H
#define _LINKEDLIST_H

#include <stdio.h>

// define a struct node
typedef int dataType;
typedef struct node
{
    dataType data;
    struct node *next;
} linkedlist, *pLinkedlist;

// fuctions
pLinkedlist ListCreate();
int ListTailInsert(pLinkedlist list, dataType value); // head
pLinkedlist ListGet(pLinkedlist list, int pos);
int ListInsert(pLinkedlist list, dataType value, int pos);
int ListShow(pLinkedlist list);
int ListElementDelete(pLinkedlist list, int pos);
pLinkedlist ListFree(pLinkedlist list);
int ListReverse(pLinkedlist list);
pLinkedlist ListAdjMax(pLinkedlist list, dataType *value);

#endif

LinkedList.c

#include <stdlib.h>
#include "LinkedList.h"
#include <errno.h>

/**
 * @brief create a linked list
 *
 * @return pLinkedlist: Address of the head node
 */
pLinkedlist ListCreate()
{
    pLinkedlist list = (pLinkedlist)malloc(sizeof(linkedlist));
    if (list == NULL)
    {
        printf("malloc error\n");
        return NULL;
    }

    list->data = 0;
    list->next = NULL;

    return list;
}

int ListTailInsert(pLinkedlist list, dataType value)
{
    if (list == NULL)
    {
        printf("TailInsert error:arg list is invalid\n");
        return -1;
    }

    // Apply for a new space
    pLinkedlist newNode = (pLinkedlist)malloc(sizeof(linkedlist));
    if (newNode == NULL)
    {
        printf("malloc error\n");
        return -1;
    }

    // update value
    newNode->data = value;
    newNode->next = NULL;

    // Find the last element of the old linked list
    pLinkedlist p = list;
    while (p->next)
    {
        p = p->next;
    }

    // update list
    p->next = newNode;

    return 0;
}

/**
 * @brief Gets the address of the element at the specified location
 *
 * @param list
 * @param pos
 * @return pLinkedlist
 */
pLinkedlist ListGet(pLinkedlist list, int pos)
{
    if (list == NULL)
    {
        printf("ListGet error:arg list is invalid\n");
        return NULL;
    }

    if (pos == -1)
    {
        return list;
    }

    pLinkedlist p = list;
    for (int i = 0; i < pos + 1; i++)
    {
        p = p->next;
        if (p == NULL)
        {
            printf("pos is invalid\n");
            return NULL;
        }
    }

    return p;
}

/**
 * @brief Insert an element into the specified position
 *
 * @param list
 * @param value
 * @param pos
 * @return int 0:success -1:failed
 */
int ListInsert(pLinkedlist list, dataType value, int pos)
{
    if (list == NULL)
    {
        printf("ListInsert error:arg list is invalid\n");
        return -1;
    }

    // Apply for a new space
    pLinkedlist newNode = (pLinkedlist)malloc(sizeof(linkedlist));
    if (newNode == NULL)
    {
        printf("malloc error\n");
        return -1;
    }

    // update value
    newNode->data = value;
    newNode->next = NULL;

    // Find the location to be inserted
    pLinkedlist lastNode = ListGet(list, pos - 1);
    if (lastNode == NULL)
    {
        printf("Insert an invalid position\n");
        return -1;
    }

    // Complete insertion operation
    newNode->next = lastNode->next;
    lastNode->next = newNode;

    return 0;
}

int ListShow(pLinkedlist list)
{
    if (list == NULL)
    {
        printf("ListShow error:arg list is invalid\n");
        return -1;
    }

    pLinkedlist p = list;
    while (p->next)
    {
        p = p->next;
        printf("%d ", p->data);
    }
    printf("\n");

    return 0;
}

int ListElementDelete(pLinkedlist list, int pos)
{
    if (list == NULL)
    {
        perror("(ListElementDelete) invalid arg list");
        return -1;
    }

    if (pos < 0)
    {
        perror("(ListElementDelete) invalid arg pos");
        return -1;
    }

    // Find the element at the current position
    pLinkedlist p = ListGet(list, pos);
    if (p == NULL)
    {
        perror("(ListElementDelete) invalid arg pos");
        return -1;
    }

    // Find the previous element of the element at the current position
    pLinkedlist q = ListGet(list, pos - 1);
    q->next = p->next;
    free(p);
    p = NULL;

    return 0;
}

pLinkedlist ListFree(pLinkedlist list)
{
    if (list == NULL)
    {
        printf("ListFree error:arg list is invalid\n");
        return list;
    }

    pLinkedlist p = list;
    while (list != NULL)
    {
        p = list;
        list = list->next;
        free(p);
    }
    p = NULL;

    return NULL;
}

int ListReverse(pLinkedlist list)
{
    pLinkedlist p, q;
    if (list == NULL)
    {
        printf("ListReverse: arg is invalid.\n");
        return -1;
    }

    if (list->next == NULL || list->next->next == NULL)
    {
        return 0;
    }

    p = list->next->next;
    list->next->next = NULL;
    while (p != NULL)
    {
        q = p;
        p = p->next;
        q->next = list->next;
        list->next = q;
    }

    return 0;
}

/**
 * @brief Find the first node with the largest sum of two adjacent elements in the entire linked list
 *
 * @param list
 * @param value sum
 * @return pLinkedlist
 */
pLinkedlist ListAdjMax(pLinkedlist list, dataType *value)
{
    int sum = 0;
    pLinkedlist p, q, r;
    if (list == NULL)
    {
        printf("ListAdjMax: arg list is invalid.\n");
        return NULL;
    }

    if (list->next == NULL || list->next->next == NULL || list->next->next->next == NULL)
    {
        return list;
    }

    p = list->next;
    q = list->next->next;
    sum = p->data + q->data;
    r = p;

    while (q->next != NULL)
    {
        p = p->next;
        q = q->next;

        if (sum < (p->data + q->data))
        {
            r = p;
            sum = p->data + q->data;
        }
    }

    *value = sum;
    return r;
}

main.c

#include <stdio.h>
#include "LinkedList.h"

void test_insert();
void test_ListGet();
void test_ListInsert();
void test_ListElementDelete();
void test_ListFree();
void test_ListReverse();
void test_ListAdjMax();

int main(int argc, char const *argv[])
{
    // test_insert();
    // test_ListGet();
    // test_ListInsert();
    // test_ListElementDelete();
    // test_ListFree();
    // test_ListReverse();
    test_ListAdjMax();
    return 0;
}

void test_insert()
{
    pLinkedlist list = ListCreate();

    ListTailInsert(list, 10);
    ListTailInsert(list, 20);
    ListTailInsert(list, 30);
    ListTailInsert(list, 40);
    ListTailInsert(list, 50);

    ListShow(list);
}

void test_ListGet()
{
    pLinkedlist list = ListCreate();

    ListTailInsert(list, 10);
    ListTailInsert(list, 20);
    ListTailInsert(list, 30);
    ListTailInsert(list, 40);
    ListTailInsert(list, 50);

    ListShow(list);

    for (int i = 0; i < 5; i++)
    {
        printf("list[%d] = %d\n", i, (ListGet(list, i))->data);
    }
}

void test_ListInsert()
{
    pLinkedlist list = ListCreate();

    ListTailInsert(list, 10);
    ListTailInsert(list, 20);
    ListTailInsert(list, 30);
    ListTailInsert(list, 40);
    ListTailInsert(list, 50);

    ListShow(list);

    printf("-------------------\n");

    ListInsert(list, 200, 1);
    ListShow(list);
}

void test_ListElementDelete()
{
    pLinkedlist list = ListCreate();

    ListTailInsert(list, 10);
    ListTailInsert(list, 20);
    ListTailInsert(list, 30);
    ListTailInsert(list, 40);
    ListTailInsert(list, 50);

    ListShow(list);

    printf("-------------------\n");

    ListElementDelete(list, 4);
    ListShow(list);
}

void test_ListFree()
{
    pLinkedlist list = ListCreate();

    ListTailInsert(list, 10);
    ListTailInsert(list, 20);
    ListTailInsert(list, 30);
    ListTailInsert(list, 40);
    ListTailInsert(list, 50);

    ListShow(list);

    list = ListFree(list);
    ListTailInsert(list, 50);
    ListShow(list);
}

void test_ListReverse()
{
    pLinkedlist list = ListCreate();

    ListTailInsert(list, 10);
    ListTailInsert(list, 20);
    ListTailInsert(list, 30);
    ListTailInsert(list, 40);
    ListTailInsert(list, 50);

    ListShow(list);

    printf("-------------------\n");

    ListReverse(list);
    ListShow(list);
}

void test_ListAdjMax()
{
    int max = 0;
    pLinkedlist list = ListCreate();

    ListTailInsert(list, 10);
    ListTailInsert(list, 20);
    ListTailInsert(list, 30);
    ListTailInsert(list, 40);
    ListTailInsert(list, 50);

    ListShow(list);

    pLinkedlist p = ListAdjMax(list, &max);
    printf("p->data = %d,max = %d", p->data, max);
}

总结

未实现的接口

1. 合并两个链表
2. 求两个链表的并集
3. 元素排序
4. 消除链表中的相同元素