双链列表插入方法实现-正在搜索哪个节点

Question

I'm reviewing data structures and using this book . When inserting a node, the list has to be traversed. But in the implementation of insert operation of a doubly-linked list DS I don't understand how can k be equal to position :

while ((k < position - 1) && temp->next!=NULL) {
    temp = temp->next;
    k++;
}


if (k!=position) {   <----------------- this will true all the time?!
    printf("Desired position does not exist\n");
}

What am I missing? Or is this a typo?

Thanks in advance!

Here is the full method implementation:

void DLLInsert(struct DLLNode **head, int data, int position) {
    int k = 1;
    struct DLLNode *temp, *newNode;
    newNode = (struct DLLNode *) malloc(sizeof( struct DLLNode ));
    if (!newNode) {
        printf("Memory Error");
        return;
    }
    newNode->data = data;
    if (position == 1) {
        newNode->next = *head;
        newNode->prev = NULL;

        if (*head) {
            (*head)->prev = newNode;
        }
        *head = newNode;
        return;
    }

    temp = *head;
    while ((k < position - 1) && temp->next!=NULL) {
        temp = temp->next;
        k++;
    }

    if (k!=position) {
        printf("Desired position does not exist\n");
    }

    newNode->next=temp->next;
    newNode->prev=temp;

    if (temp->next) {
        temp->newNode->prev=newNode;
    }

    temp->next=newNode;
    return;
}

Answer 1

I think you don't miss something - k!=position will always be true at this point in the code; the only chance that k!=position would be true is when position==1 , but in this case the function returns before reaching the if . The check should rather be if(temp==NULL) .

There are some other issues, which let me think that the author did not test (actually not even compile) the code:

temp->newNode->prev=newNode;  // will this compile? I don't think that there's a member named `newNode`.

The code will crash if *head points to NULL , but one passes a position > 1 ;