input filestream to a doubly linked list

This is a discussion on input filestream to a doubly linked list within the C++ Programming forums, part of the General Programming Boards category; Coded...

  1. #1
    Registered User
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    input filestream to a doubly linked list

    Coded
    Last edited by Undying Mirai; 06-26-2006 at 06:47 AM. Reason: Already done it

  2. #2
    Code Goddess Prelude's Avatar
    Join Date
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    Posts
    9,796
    To append into a double linked list, you need to reset any links that change, that means the next link of the tail and the previous link of the new tail:
    Code:
    temp = new link;
    temp->next = 0;
    temp->prev = tail;
    tail->next = temp;
    tail = tail->next;
    To prepend, you basically do the same thing reversed:
    Code:
    temp = new link;
    temp->next = head;
    temp->prev = 0;
    head->prev = temp;
    head = temp;
    To insert, you have four links to fix:
    Code:
    temp = new link;
    temp->next = after;
    temp->prev = before;
    before->next = temp;
    after->prev = temp;
    Naturally, you don't always need unique pointers to each node that changes. A lot of the time you can use next or prev chains to avoid temporary variables:
    Code:
    tail->next = new link;
    tail->next->next = 0;
    tail->next->prev = tail;
    tail = tail->next;
    Code:
    head->prev = new link;
    head->prev->next = head;
    head->prev->prev = 0;
    head = temp;
    Code:
    temp = new link;
    temp->next = before->next;
    temp->prev = before;
    before->next->prev = temp;
    before->next = temp;
    
    // or
    
    temp = new link;
    temp->next = after;
    temp->prev = after->prev;
    after->prev->next = temp;
    after->prev = temp;
    p.s. Don't ever delete your post's content. Other people can learn from your question and any answers to it.
    My best code is written with the delete key.

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