44 lines
1.3 KiB
CoffeeScript
44 lines
1.3 KiB
CoffeeScript
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# Roughly following https://learnersbucket.com/tutorials/data-structures/implement-deque-data-structure-in-javascript/
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export default class Deque
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constructor: ->
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@clear()
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insertLeft: (elm) -> # Add an item on the left
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if @left_full > 0
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@items[--@left_full] = elm
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else
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@right_open++
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@items.unshift elm
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insertRight: (elm) -> # Add an item on the right of the list
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@items[@right_open++] = elm
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removeLeft: -> # Remove the item from the left
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@nonempty() and @items[@left_full++]
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removeRight: -> # Remove the item from the right
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@nonempty() and @items[--@right_open]
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left: -> # Peek the leftmost element
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@nonempty and @items[@left_full]
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right: -> # Peek the last element
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@nonempty and @items[@right_open - 1]
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nonempty: -> # Returns null if no elements
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(@right_open > @left_full) or null
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empty: -> # Returns null if any elements
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(@right_open is @left_full) or null
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size: -> # Number of elements
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@right_open - @left_full
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clear: -> # Remove all elements
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@right_open = @left_full = 0
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@items = []
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toString: ->
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"<#{@items[@left...@right].join(",")}>"
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