c - 单向链表操作在特定位置插入

Question

我编写了一个程序来执行单链表操作在特定位置插入 现在没有节点，当我给问题输入:3 输入要插入的位置显示运行时错误

void insert_pos()
    {
        struct node * temp, *loc;
        int item,pos,len;
        printf("enter the position to be insertd :");
        scanf("%d", &pos);
        if (pos == 1)
        {
            insert_beg();
        }
        else
        {
            len = length();
            if (start == NULL)
            {
                insert_beg();
            }
            else if (pos > len)
            {
                insert_end();
            }
            else
            {
                newnode = (struct node *)malloc(sizeof(struct node));
                printf("enter the data :");
                scanf("%d", &item);
                newnode->data = item;
                int i;
                temp = start;
                loc = temp->next;
                for (i = 1; i < pos - 1; i++)
                {
                    temp = temp->next;
                    loc = loc->next;
                }
                temp->next = newnode;
                newnode->next = loc;
            }
        }
    }
    int length()
    {
        int k = 1;
        struct node * temp;
        while (temp->next != NULL)
        {
            temp = temp->next;
            k++;
        }
        return k;
    }

输出

1.insert @ beg
2.insert @ end
3.insert @ perticular pos
4.display
5.exit
enter your option :3
enter the position to be inserted :3

现在弹出一个窗口说调试错误请帮助我

Answer 1

问题出在温度未初始化

int length()
{
    int k = 1;
    struct node * temp;
    while (temp->next != NULL)
    {
        temp = temp->next;
        k++;
    }
    return k;
}

解决方法是分配 temp = start;

更正程序

int length()
{
    int k = 1;
    struct node * temp;
    temp=start;  // start is a global variable
    while (temp->next != NULL)
    {
        temp = temp->next;
        k++;
    }
    return k;
}

感谢大家的提示!!!