feat: add Swift codes for heap article (#306)

* feat: add Swift codes for heap article

* Update heap.md

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/swift/Package.swift

@@ -27,6 +27,7 @@ let package = Package(
         .executable(name: "binary_tree_dfs", targets: ["binary_tree_dfs"]),
         .executable(name: "binary_search_tree", targets: ["binary_search_tree"]),
         .executable(name: "avl_tree", targets: ["avl_tree"]),
+        .executable(name: "my_heap", targets: ["my_heap"]),
     ],
     targets: [
         .target(name: "utils", path: "utils"),
@@ -52,5 +53,6 @@ let package = Package(
         .executableTarget(name: "binary_tree_dfs", dependencies: ["utils"], path: "chapter_tree", sources: ["binary_tree_dfs.swift"]),
         .executableTarget(name: "binary_search_tree", dependencies: ["utils"], path: "chapter_tree", sources: ["binary_search_tree.swift"]),
         .executableTarget(name: "avl_tree", dependencies: ["utils"], path: "chapter_tree", sources: ["avl_tree.swift"]),
+        .executableTarget(name: "my_heap", dependencies: ["utils"], path: "chapter_heap", sources: ["my_heap.swift"]),
     ]
 )

codes/swift/chapter_heap/my_heap.swift

@@ -0,0 +1,167 @@
+/**
+ * File: my_heap.swift
+ * Created Time: 2023-01-28
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+import utils
+
+class MaxHeap {
+    private var maxHeap: [Int]
+
+    /* 构造函数，建立空堆 */
+    init() {
+        maxHeap = []
+    }
+
+    /* 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)
+        }
+    }
+
+    /* 获取左子结点索引 */
+    private func left(i: Int) -> Int {
+        2 * i + 1
+    }
+
+    /* 获取右子结点索引 */
+    private func right(i: Int) -> Int {
+        2 * i + 2
+    }
+
+    /* 获取父结点索引 */
+    private func parent(i: Int) -> Int {
+        (i - 1) / 2 // 向下整除
+    }
+
+    /* 交换元素 */
+    private func swap(i: Int, j: Int) {
+        maxHeap.swapAt(i, j)
+    }
+
+    /* 获取堆大小 */
+    func size() -> Int {
+        maxHeap.count
+    }
+
+    /* 判断堆是否为空 */
+    func isEmpty() -> Bool {
+        size() == 0
+    }
+
+    /* 访问堆顶元素 */
+    func peek() -> Int {
+        maxHeap[0]
+    }
+
+    /* 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)
+    }
+
+    /* 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
+        }
+    }
+
+    /* 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
+    }
+
+    /* 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
+        }
+    }
+
+    /* 打印堆（二叉树） */
+    func print() {
+        let queue = maxHeap
+        PrintUtil.printHeap(queue: queue)
+    }
+}
+
+@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()
+
+        /* 获取堆顶元素 */
+        var peek = maxHeap.peek()
+        print("\n堆顶元素为 \(peek)")
+
+        /* 元素入堆 */
+        let val = 7
+        maxHeap.push(val: val)
+        print("\n元素 \(val) 入堆后")
+        maxHeap.print()
+
+        /* 堆顶元素出堆 */
+        peek = maxHeap.poll()
+        print("\n堆顶元素 \(peek) 出堆后")
+        maxHeap.print()
+
+        /* 获取堆大小 */
+        let size = maxHeap.size()
+        print("\n堆元素数量为 \(size)")
+
+        /* 判断堆是否为空 */
+        let isEmpty = maxHeap.isEmpty()
+        print("\n堆是否为空 \(isEmpty)")
+    }
+}

codes/swift/utils/PrintUtil.swift

@@ -74,4 +74,12 @@ public enum PrintUtil {
             print("\(key) -> \(value)")
         }
     }
+
+    public static func printHeap(queue: [Int]) {
+        print("堆的数组表示：", terminator: "")
+        print(queue)
+        print("堆的树状表示：")
+        let root = TreeNode.listToTree(list: queue)
+        printTree(root: root)
+    }
 }