链表C语言实现

#include<stdio.h>#include<stdlib.h>typedef struct Node{    int a;    struct Node* pNext;}Node;Node* top = NULL;Node* end = NULL;void addNode(int a){    Node* node = (Node*)malloc (sizeof(Node));    node->pNext = NULL;    node->a = a;    if(top==NULL)    {        top = node;    }    else    {        end->pNext = node;    }    end = node;}void delNode(int a){    Node *pptop = top;    if(top->a==a)    {        Node* node=top;        top = top->pNext;        free(node);        return;    }    while(pptop->pNext)    {        if(pptop->pNext->a == a)        {            Node* node=pptop->pNext;            pptop->pNext = pptop->pNext->pNext;            free(node);            return;        }        pptop = pptop->pNext;    }}Node* findNode(int a){    Node* pptop = top;    while(pptop)    {        if(pptop->a==a)        {            return pptop;        }        pptop=pptop->pNext;    }    return NULL;}void showNode(){    Node* pptop = top;    while(pptop)    {        printf("%d\n",pptop->a);        pptop = pptop->pNext;     }}int main(){    int a=3;    while(a--)    {        addNode(a);    }    showNode();    delNode(1);    showNode();    return 0;}