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feat: add Swift codes for heap article (krahets#306)
* feat: add Swift codes for heap article * Update heap.md --------- Co-authored-by: Yudong Jin <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,167 @@ | ||
| /** | ||
| * File: my_heap.swift | ||
| * Created Time: 2023-01-28 | ||
| * Author: nuomi1 ([email protected]) | ||
| */ | ||
|
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| import utils | ||
|
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| class MaxHeap { | ||
| private var maxHeap: [Int] | ||
|
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| /* 构造函数，建立空堆 */ | ||
| init() { | ||
| maxHeap = [] | ||
| } | ||
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| /* 构造函数，根据输入列表建堆 */ | ||
| init(nums: [Int]) { | ||
| // 将列表元素原封不动添加进堆 | ||
| maxHeap = nums | ||
| // 堆化除叶结点以外的其他所有结点 | ||
| for i in stride(from: parent(i: size() - 1), through: 0, by: -1) { | ||
| siftDown(i: i) | ||
| } | ||
| } | ||
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| /* 获取左子结点索引 */ | ||
| private func left(i: Int) -> Int { | ||
| 2 * i + 1 | ||
| } | ||
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| /* 获取右子结点索引 */ | ||
| private func right(i: Int) -> Int { | ||
| 2 * i + 2 | ||
| } | ||
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| /* 获取父结点索引 */ | ||
| private func parent(i: Int) -> Int { | ||
| (i - 1) / 2 // 向下整除 | ||
| } | ||
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| /* 交换元素 */ | ||
| private func swap(i: Int, j: Int) { | ||
| maxHeap.swapAt(i, j) | ||
| } | ||
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| /* 获取堆大小 */ | ||
| func size() -> Int { | ||
| maxHeap.count | ||
| } | ||
|
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| /* 判断堆是否为空 */ | ||
| func isEmpty() -> Bool { | ||
| size() == 0 | ||
| } | ||
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| /* 访问堆顶元素 */ | ||
| func peek() -> Int { | ||
| maxHeap[0] | ||
| } | ||
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| /* 元素入堆 */ | ||
| func push(val: Int) { | ||
| // 添加结点 | ||
| maxHeap.append(val) | ||
| // 从底至顶堆化 | ||
| siftUp(i: size() - 1) | ||
| } | ||
|
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| /* 从结点 i 开始，从底至顶堆化 */ | ||
| private func siftUp(i: Int) { | ||
| var i = i | ||
| while true { | ||
| // 获取结点 i 的父结点 | ||
| let p = parent(i: i) | ||
| // 当“越过根结点”或“结点无需修复”时，结束堆化 | ||
| if p < 0 || maxHeap[i] <= maxHeap[p] { | ||
| break | ||
| } | ||
| // 交换两结点 | ||
| swap(i: i, j: p) | ||
| // 循环向上堆化 | ||
| i = p | ||
| } | ||
| } | ||
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| /* 元素出堆 */ | ||
| func poll() -> Int { | ||
| // 判空处理 | ||
| if isEmpty() { | ||
| fatalError("堆为空") | ||
| } | ||
| // 交换根结点与最右叶结点（即交换首元素与尾元素） | ||
| swap(i: 0, j: size() - 1) | ||
| // 删除结点 | ||
| let val = maxHeap.remove(at: size() - 1) | ||
| // 从顶至底堆化 | ||
| siftDown(i: 0) | ||
| // 返回堆顶元素 | ||
| return val | ||
| } | ||
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| /* 从结点 i 开始，从顶至底堆化 */ | ||
| private func siftDown(i: Int) { | ||
| var i = i | ||
| while true { | ||
| // 判断结点 i, l, r 中值最大的结点，记为 ma | ||
| let l = left(i: i) | ||
| let r = right(i: i) | ||
| var ma = i | ||
| if l < size(), maxHeap[l] > maxHeap[ma] { | ||
| ma = l | ||
| } | ||
| if r < size(), maxHeap[r] > maxHeap[ma] { | ||
| ma = r | ||
| } | ||
| // 若结点 i 最大或索引 l, r 越界，则无需继续堆化，跳出 | ||
| if ma == i { | ||
| break | ||
| } | ||
| // 交换两结点 | ||
| swap(i: i, j: ma) | ||
| // 循环向下堆化 | ||
| i = ma | ||
| } | ||
| } | ||
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| /* 打印堆（二叉树） */ | ||
| func print() { | ||
| let queue = maxHeap | ||
| PrintUtil.printHeap(queue: queue) | ||
| } | ||
| } | ||
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| @main | ||
| enum MyHeap { | ||
| /* Driver Code */ | ||
| static func main() { | ||
| /* 初始化大顶堆 */ | ||
| let maxHeap = MaxHeap(nums: [9, 8, 6, 6, 7, 5, 2, 1, 4, 3, 6, 2]) | ||
| print("\n输入列表并建堆后") | ||
| maxHeap.print() | ||
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| /* 获取堆顶元素 */ | ||
| var peek = maxHeap.peek() | ||
| print("\n堆顶元素为 \(peek)") | ||
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| /* 元素入堆 */ | ||
| let val = 7 | ||
| maxHeap.push(val: val) | ||
| print("\n元素 \(val) 入堆后") | ||
| maxHeap.print() | ||
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| /* 堆顶元素出堆 */ | ||
| peek = maxHeap.poll() | ||
| print("\n堆顶元素 \(peek) 出堆后") | ||
| maxHeap.print() | ||
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| /* 获取堆大小 */ | ||
| let size = maxHeap.size() | ||
| print("\n堆元素数量为 \(size)") | ||
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| /* 判断堆是否为空 */ | ||
| let isEmpty = maxHeap.isEmpty() | ||
| print("\n堆是否为空 \(isEmpty)") | ||
| } | ||
| } |
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