38 lines
824 B
Swift
38 lines
824 B
Swift
//
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// Created by Jiandan on 2018/10/12.
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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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struct StackBasedOnLinkedList<Element>: Stack {
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private var head = Node<Element>() // 哨兵结点，不存储内容
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// MARK: Protocol: Stack
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var isEmpty: Bool { return head.next == nil }
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var size: Int {
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var count = 0
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while head.next != nil {
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count += 1
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}
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return count
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}
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var peek: Element? { return head.next?.value }
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func push(newElement: Element) -> Bool {
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let node = Node(value: newElement)
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node.next = head.next
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head.next = node
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return true
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}
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func pop() -> Element? {
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let node = head.next
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head.next = node?.next
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return node?.value
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}
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}
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