62 lines
1.4 KiB
Swift
62 lines
1.4 KiB
Swift
//
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// Created by Jiandan on 2018/10/11.
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// Copyright (c) 2018 Jiandan. All rights reserved.
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//
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import Foundation
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/// 循环队列
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struct CircularQueue<Element>: Queue {
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/// 数组
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private var items: [Element]
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/// 数组最大长度
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private var capacity = 0
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/// 队头下标
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private var head = 0
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/// 队尾下标
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private var tail = 0
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/// 构造方法
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/// - parameter defaultElement: 默认元素
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/// - parameter capacity: 数组长度
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init(defaultElement: Element, capacity: Int) {
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self.capacity = capacity
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items = [Element](repeating: defaultElement, count: capacity)
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}
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// MARK: Protocol: Queue
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var isEmpty: Bool { return head == tail }
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var size: Int {
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if tail >= head {
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return tail - head
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} else {
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return (tail + 1) + (capacity - head)
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}
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}
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var peek: Element? { return isEmpty ? nil : items[head] }
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mutating func enqueue(newElement: Element) -> Bool {
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// 整个队列都占满了
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if (tail + 1) % capacity == head {
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return false
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}
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items[tail] = newElement
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tail = (tail + 1) % capacity
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return true
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}
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mutating func dequeue() -> Element? {
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if isEmpty {
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return nil
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}
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let item = items[head]
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head = (head + 1) % capacity
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return item
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}
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}
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