数据结构中双向链表中数据的插入

Question

在写c语言中双向链表时，每当运行到输入函数都会报错，显示head是空指针。不知道到底错在哪，请各位指点指点。

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
struct DoubleList {
    int element;
    struct DoubleList* next;
    struct DoubleList* prior;
};
typedef struct DoubleList* List;
void initDoubleList(List head)
{
    head->next = head->prior = NULL;
     
}
int insertDoubleList(List head, int element, int index) {
    if (index < 1)
        return 0;
    while (--index)
    {
        head = head->next;
        if (head == NULL)
            return 0;
    }
    List node = malloc(sizeof(struct DoubleList));
    if (node == NULL)
        return 0;
    node->element = element;
    
    if (head->next!=NULL)
    {
        head->next->prior = node;
        node->next = head->next;

    }
    else
    {
        node->next == NULL;

    }
    
    
    head->next = node;
    node->prior = head;
    return 1;
}
void print(List head)
{
    
    while (head)
    {
        head = head->next;
        printf("%d", head->element);

    }
}
int main()
{
    struct DoubleList head;
    initDoubleList(&head);
    for (int i = 1; i <= 3; i++)
        insertDoubleList(&head, i * 100, 1);
    
    print(&head);
    List node = &head;
    
    return 0;
}

Answer 1

 發現兩個錯誤：

    } else {
        // Bug 1，不是 == 
        node->next = NULL;
    }


void print(List head) {
    while (head) {
        head = head->next;

        // Bug 2，如果沒有這個，會宕機。
        if( head == NULL ) break;

        printf("%d \n", head->element);
    }
}