141 lines
3.9 KiB
Kotlin
141 lines
3.9 KiB
Kotlin
/*
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* MIT License
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*
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* Copyright (c) 2019 norangebit
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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package it.norangeb.algorithms.datastructures.queue
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import arrow.core.None
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import arrow.core.Option
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import arrow.core.toOption
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class ResizingArrayQueue<T>(capacity: Int = DEFAULT_CAPACITY) : Queue<T> {
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private var queue: Array<T?> = arrayOfNulls<Any>(capacity) as Array<T?>
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private var size = 0
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private var tail = 0
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private var head = 0
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override fun isEmpty(): Boolean = size == 0
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private fun isFull(): Boolean = queue.size == size
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override fun size(): Int = size
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override fun enqueue(elem: T) {
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if (isFull())
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resizeArray(size * RESIZE_FACTOR)
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queue[tail] = elem
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tail = (tail + 1) % queue.size
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size++
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}
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override fun dequeue(): Option<T> {
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val elem = peek()
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if (elem is None)
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return elem
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queue[head] = null
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head = (head + 1) % queue.size
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size--
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if (isOneQuarterFull())
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resizeArray(queue.size / RESIZE_FACTOR)
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return elem
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}
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override fun peek(): Option<T> {
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if (isEmpty())
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return None
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return queue[head].toOption()
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}
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private fun resizeArray(capacity: Int) {
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val copy: Array<T?> = arrayOfNulls<Any>(capacity) as Array<T?>
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when {
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head >= tail -> {
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for (i in head until queue.size)
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copy[i - head] = queue[i]
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val alreadyInsert = queue.size - head
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for (i in 0 until tail)
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copy[i + alreadyInsert] = queue[i]
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}
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else ->
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for (i in head until tail)
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copy[i - head] = queue[i]
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}
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queue = copy
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head = 0
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tail = size
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}
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private fun isOneQuarterFull(): Boolean = size == queue.size / 4 &&
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size > 0
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override fun forEach(action: (T) -> Unit) {
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for (elem in queue)
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if (elem != null)
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action(elem)
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}
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override fun <A> map(transform: (T) -> A): Queue<A> {
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val transformedQueue: Array<A?> = arrayOfNulls<Any>(queue.size) as Array<A?>
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for (i in 0 until queue.size) {
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val elem = queue[i]
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if (elem == null)
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transformedQueue[i] = null
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else
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transformedQueue[i] = transform(elem)
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}
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return ResizingArrayQueue(transformedQueue, head, tail, size)
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}
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override fun clean() {
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queue = arrayOfNulls<Any>(DEFAULT_CAPACITY) as Array<T?>
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size = 0
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tail = 0
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head = 0
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}
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private constructor(queue: Array<T?>, head: Int, tail: Int, size: Int) : this() {
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this.queue = queue
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this.head = head
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this.tail = tail
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this.size = size
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}
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companion object {
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const val RESIZE_FACTOR = 2
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const val DEFAULT_CAPACITY = 2
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}
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} |