Two ways to create one-way linked lists in the data structure learning series

• Method 1:
• By 返回值returning the requested one 头结点所在的内存空间首地址, that is, creating the head node of the one-way linked list, the code is as follows:
• Sample code:

node_t *create_link_node_1(){
    
    

    node_t *phead = (node_t *)malloc(sizeof(node_t));
    if(NULL == phead){
    
    

        printf("内存分配失败\n");

        exit(-1);

    }
    //或者memset(phead, 0, sizeof(node_t));
    phead->data = -1;
    phead->next = NULL;

    return phead;

}

• Precautions:
• 1. After allocating the memory address space of the head node, be sure to check 内存分配是否成功;
• 2. If the memory allocation of the head node fails, it needs to be used shell命令exit(-1)退出;
• 3. For the one-way linked list 每个结点都有数据域和指针域, and 头结点的数据域可以不储存任何数据for the head node 数据域in this function, 被赋值 -1;
• 4. For the head node 指针域被赋值 NULL, it represents the one-way linked list at this time 只有一个头结点;
• Method 2:
• The method used to 地址传参create the head node of the one-way linked list, the code is as follows:
• Sample code:

int create_link_node_2(node_t **phead,int data){
    
    

    if(NULL == phead){
    
    


        printf("入参为NULL\n");

        return -1;

    }

    *phead = (node_t *)malloc(sizeof(node_t));

    if(NULL == *phead){
    
    


        printf("内存分配失败\n");

        return -1;

    }
     //或者memset(*phead, 0, sizeof(node_t));
    (*phead)->data = data;
    (*phead)->next = NULL;

    return 0;

}

• Precautions:
• 1. The parameter passed in must be 二级指针变量, because 二级指针用来存储一级指针变量的地址, namely 所申请的单向链表头结点在内存空间的地址;
• 2. After the formal parameters are passed into the function function that creates the head node of the one-way linked list, it must be done 入参合理性检查;
• 3. Same as method 1, after allocating the memory address space of the head node, be sure to check 内存分配是否成功;
• 4. Head node 数据域被赋值 -1;
• 5. Head node 指针域被赋值 NULL;