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4.3: Bidirectional Lists

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    49277
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    Sometimes we want Data Structures/List Structures to move backward in a list too. A Bidirectional List allows the list to be searched forwards and backwards. A Bidirectional list implements an additional iterator function, move-previous().

    Bidirectional List<item-type> ADT

    get-begin():Bidirectional List Iterator<item-type>

    Returns the list iterator (we'll define this soon) that represents the first element of the list. Runs in \(O(1)\) time.

    get-end():Bidirectional List Iterator<item-type>

    Returns the list iterator that represents one element past the last element in the list. Runs in \(O(1)\) time.

    insert(iter:Bidirectional List Iterator<item-type>, new-item:item-type)

    Adds a new element immediately before iter. Runs in \(O(N)\) time.

    remove(iter:Bidirectional List Iterator<item-type>)

    Removes the element immediately referred to by iter. After this call, iter will refer to the next element in the list. Runs in \(O(N)\) time.

    is-empty():Boolean

    True iff there are no elements in the list. Has a default implementation. Runs in \(O(1)\) time.

    get-size():Integer

    Returns the number of elements in the list. Has a default implementation. Runs in \(O(N)\) time.

    get-nth(n:Integer):item-type

    Returns the nth element in the list, counting from 0. Has a default implementation. Runs in \(O(N)\) time.

    set-nth(n:Integer, new-value:item-type)

    Assigns a new value to the nth element in the list, counting from 0. Has a default implementation. Runs in \(O(N)\) time.

    Bidirectional List Iterator<item-type> ADT

    get-value():item-type

    Returns the value of the list element that this iterator refers to. Undefined if the iterator is past-the-end.

    set-value(new-value:item-type)

    Assigns a new value to the list element that this iterator refers to. Undefined if the iterator is past-the-end.

    move-next()

    Makes this iterator refer to the next element in the list. Undefined if the iterator is past-the-end.

    move-previous()

    Makes this iterator refer to the previous element in the list. Undefined if the iterator refers to the first list element.

    equal(other-iter:List Iterator<item-type>):Boolean

    True iff the other iterator refers to the same list element as this iterator.

    All operations run in \(O(1)\) time.


    This page titled 4.3: Bidirectional Lists is shared under a CC BY-SA license and was authored, remixed, and/or curated by Wikibooks - Data Structures (Wikipedia) .

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