C语言单链表增删改查基本操作

C语言单链表增删改查基本操作

#include <stdio.h>
#include <malloc.h>
#define LEN sizeof(NODE)

typedef struct _NODE//节点声明
{
    int val;
    struct _NODE* next;
} NODE, *PNODE;

void print(PNODE head){//打印所有节点
    while (head)
    {
        printf("%3d",head->val);
        head = head->next;
    }
    printf("\n");
}

void insertHead(PNODE *pHead, int val){//头插法
    PNODE n = (PNODE)malloc(LEN);
    n->val = val;
    n->next = *pHead;
    *pHead = n;
}

void insertTail(PNODE *pHead, int val){//尾插法
    PNODE t = *pHead;
    PNODE n = (PNODE)malloc(LEN);
    n->val = val;
    n->next = NULL;
    if (*pHead == NULL)
    {
        n->next = *pHead;
        *pHead = n;
    }else{
        while (t->next)
        {
            t = t->next;
        }
        t->next = n;
    }
}

void deleteHead(PNODE *pHead){//删除头
    if (*pHead == NULL)
    {
        return;
    }
    else
    {
        PNODE t = *pHead;
        *pHead = (*pHead)->next;
        free(t);
    }
}

void deleteTail(PNODE *pHead){//删除尾
    PNODE t = *pHead;
    if (t == NULL)
    {
        return;
    }
    else if (t->next == NULL)
    {
        free(t);
        *pHead = NULL;
    }
    else{        
        while (t->next->next != NULL)
        {
            t = t->next;
        }
        free(t->next);
        t->next = NULL;
    }
}

PNODE findByVal(PNODE head, int val){//根据值找到满足条件的第一个节点
    while (head != NULL && head->val != val)
    {
        head = head->next;
    }
    return head;
}

PNODE findByIndex(PNODE head, int index){//根据索引找节点
    if (index == 1)
    {
        return head;
    }
    else
    {
        int c = 1;
        while (head != NULL && index != c)
        {
            head = head->next;
            c++;
        }
    }
    return head;
}

void insertByIndex(PNODE *pHead, int index, int val){//根据索引插入节点
    if (index == 1)
    {
        insertHead(pHead, val);
    }
    else
    {
        PNODE t = findByIndex(*pHead,index - 1);
        if (t == NULL)
        {
            return;
        }
        else
        {
            PNODE n = t->next;
            t->next = (PNODE)malloc(LEN);
            t->next->next = n;
            t->next->val = val;
        }
    }
}

void deleteByIndex(PNODE *pHead, int index)//根据结点索引删除结点
{
    if (index == 1)
    {
        deleteHead(pHead);
    }
    else
    {
        PNODE t= findByIndex(*pHead, index - 1);
        if (t == NULL || t->next == NULL)
        {
            return;
        }else{
            PNODE n = t->next->next;
            free(t->next);
            t->next = n;
        }
    }
}

void deleteByVal(PNODE *pHead, int val)//根据值删掉第一个满足条件的
{
    if (*pHead == NULL)//如果空表退出
    {
        return;
    }
    else
    {
        if ((*pHead)->val == val)//如果第一个就是，删头
        {
            deleteHead(pHead);
        }
        else
        {
            PNODE t = *pHead;
            while (t->next != NULL && t->next->val != val)//遍历，若t的next为空或者next是要找的节点则退出
            {
                t = t->next;
            }
            if (t->next)//如果t指向要找的结点的上一个节点
            {
                PNODE n = t->next->next;//删除要找的结点
                free(t->next);
                t->next = n;
            }
        }
    }
}

void clear(PNODE *pHead)//清除链表
{
    while ((*pHead) != NULL)
    {
        deleteHead(pHead);//从头删除
    }
}

void main()
{
    PNODE head = NULL;

    insertTail(&head,1);
    deleteHead(&head);
    insertTail(&head,2);
    insertTail(&head,3);
    insertTail(&head,4);
    insertTail(&head,5);
    insertTail(&head,6);

    print(head);
    insertByIndex(&head, 6, 9);
    print(head);
    //deleteByIndex(&head,3);
    deleteByVal(&head, 2);
    print(head);
    clear(&head);
    print(head);
    insertByIndex(&head,1,12);
    print(head);
}