双向链表--

内存泄漏：当while（1）一直运行时，操作系统一直被申请空间，最终无空间可申请，造成内存泄漏。所以可以在堆区手动申请空间，在用完后手动释放

测试是否存在内存泄漏：

安装命令：sudo apt-get install valgrind


执行命令：先编译，然后 valgrind ./a.out

双向链表的节点与链表对象

typedef struct stu
{
    int id;
    char name[32];
    int score;
}Datatype;

typedef struct dnode
{
    Datatype data;
    struct dnode *ppre;
    struct dnode *pnext;


}DLink_Node_t;

typedef struct dlink
{
    DLink_Node_t *phead;
    int clen;
    


}DLink_t;

创建一个链表

DLink_t * create_dlink()
{
    DLink_t *pdlink = malloc(sizeof(DLink_t));
    if(pdlink == NULL)
    {
        perror("fail malloc");
        return NULL;

    }
    pdlink->phead = NULL;
    pdlink->clen = 0;

    return pdlink;

}

判断链表是否为空

int is_empty_dlink(DLink_t *pdlink)
{
    return NULL == pdlink->phead;


}

遍历

void printlist(DLink_t *pdlink,int dir)
{
    if(is_empty_dlink(pdlink))
    {
    return;
    }
    DLink_Node_t *p = pdlink->phead;
    if(dir)
    {
        while(p != NULL)
        {
            printf("%d\n%s\n%d\n",p->data.id,p->data.name,p->data.score);
            p=p->pnext;
        }
    }
    else
    {
        while(p->pnext != NULL)
        {
            p = p->pnext;
        }
        while(p != NULL)
        {
            printf("%d\n%s\n%d\n",p->data.id,p->data.name,p->data.score);
            p = p->ppre;
        }
    }
    printf("\n");
}

头插

//头插
int push_dlink_head(DLink_t *pdlink,Datatype data)
{
    DLink_Node_t *pnode = malloc(sizeof(DLink_Node_t));
    if(NULL == pnode)
    {
        perror("fail malloc");
        return -1;
    }
    pnode->data = data;
    pnode->ppre = NULL;
    pnode->pnext = NULL;
    if(is_empty_dlink(pdlink))
    {
        pdlink->phead = pnode;
    }
    else
    {
        pnode->pnext = pdlink->phead;
        pdlink->phead->ppre = pnode;
        pdlink->phead = pnode;
    }
    pdlink->clen++;
    return 0;
}

尾插

//尾插
int push_dlink_back(DLink_t *pdlink,Datatype data)
{
    DLink_Node_t *p = pdlink->phead;

    DLink_Node_t *pnode = malloc(sizeof(DLink_Node_t));
    if(NULL == pnode)
    {
        perror("fail malloc");
        return -1;
    }
    pnode->data = data;
    pnode->ppre = NULL;
    pnode->pnext = NULL;
    if(is_empty_dlink(pdlink))
    {
        pdlink->phead = pnode;
    }

    else
    {
        while(p->pnext != NULL)
        {
            p=p->pnext; 
        }

        p->pnext = pnode;
        pnode->ppre = p;
        pnode->pnext = NULL;    
    }

    pdlink->clen++;
    return 0;
}

头删

//头删
void pop_front_dlink(DLink_t *pdlink)
{
    DLink_Node_t *p = pdlink->phead;
    if(!is_empty_dlink(pdlink))
    {
        if(p->pnext== NULL)
        {
            pdlink->phead =NULL;

            free(p);
        }
        else
        {
            pdlink->phead = p->pnext;
            p->pnext->ppre=NULL;
            free(p);
        }
        pdlink->clen--;
    }


}

尾删

//尾删
void pop_back_dlink(DLink_t *pdlink)
{

    DLink_Node_t *p = pdlink->phead;
    if(p->pnext == NULL)
    {
        pop_front_dlink(pdlink);
    
    }
    else
    {
        while(p->pnext != NULL)
        {
            p=p->pnext;
        }
        p->ppre->pnext=NULL;
        free(p);
        pdlink->clen--;
    }
}

查找

//查找
DLink_Node_t *select_dlink(DLink_t *pdlink,char *s)
{
    DLink_Node_t *p = pdlink->phead;
    while(p != NULL)
    {
        if(strcmp(p->data.name,s)==0)
        {
            return p;
        
        }

        p=p->pnext;
    
    }

}

修改

//修改


int change_dlink_data(DLink_t *pdlink,char *s,int m)
{
    DLink_Node_t *p = select_dlink(pdlink,s);

    p->data.score = m;
    return 0;
}

销毁

//销毁
void destory_dlink(DLink_t *pdlink)
{
    while(!is_empty_dlink(pdlink))
    {
        pop_front_dlink(pdlink);
    
    }
    free(pdlink);


}

主函数调用

#include"head.h"
#include"doublelink.h"

int main(int argc,const char *argv[])
{
    DLink_t *pdlink = create_dlink();
    if(pdlink == NULL)
    {
        return -1;
    
    }
    Datatype stus[] = {{1, "zhangsan", 99},
						{2, "lisi", 85},
						{3, "wanger", 88},
						{4, "zhaowu", 65},
						{5, "lijiu", 78}};

	push_dlink_head(pdlink, stus[0]);
	push_dlink_head(pdlink, stus[1]);
	push_dlink_head(pdlink, stus[2]);
    push_dlink_back(pdlink,stus[3]);
    push_dlink_back(pdlink,stus[4]);
    printlist(pdlink,1);
    printlist(pdlink,0);
    pop_front_dlink(pdlink);
    pop_back_dlink(pdlink);

   // pop_back_dlink(pdlink);
   // DLink_Node_t *p = select_dlink(pdlink,"lisi");
   // printf("%d\n",p->data.score);
  //  change_dlink_data(pdlink,"lisi",75);
  //  printf("----------%d\n",pdlink->clen);

   // push_dlink_back(pdlink,stus[4]);
   //  printlist(pdlink,1);
    // printlist(pdlink,0);
     destory_dlink(pdlink);
    return 0;
}