feat: add Swift codes for heap_sort article (#520)

codes/swift/Package.swift

@@ -52,6 +52,7 @@ let package = Package(
         .executable(name: "insertion_sort", targets: ["insertion_sort"]),
         .executable(name: "quick_sort", targets: ["quick_sort"]),
         .executable(name: "merge_sort", targets: ["merge_sort"]),
+        .executable(name: "heap_sort", targets: ["heap_sort"]),
         .executable(name: "bucket_sort", targets: ["bucket_sort"]),
         .executable(name: "counting_sort", targets: ["counting_sort"]),
         .executable(name: "radix_sort", targets: ["radix_sort"]),
@@ -115,6 +116,7 @@ let package = Package(
         .executableTarget(name: "insertion_sort", path: "chapter_sorting", sources: ["insertion_sort.swift"]),
         .executableTarget(name: "quick_sort", path: "chapter_sorting", sources: ["quick_sort.swift"]),
         .executableTarget(name: "merge_sort", path: "chapter_sorting", sources: ["merge_sort.swift"]),
+        .executableTarget(name: "heap_sort", path: "chapter_sorting", sources: ["heap_sort.swift"]),
         .executableTarget(name: "bucket_sort", path: "chapter_sorting", sources: ["bucket_sort.swift"]),
         .executableTarget(name: "counting_sort", path: "chapter_sorting", sources: ["counting_sort.swift"]),
         .executableTarget(name: "radix_sort", path: "chapter_sorting", sources: ["radix_sort.swift"]),

codes/swift/chapter_sorting/heap_sort.swift

@@ -0,0 +1,55 @@
+/**
+ * File: heap_sort.swift
+ * Created Time: 2023-05-28
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+/* 堆的长度为 n ，从节点 i 开始，从顶至底堆化 */
+func siftDown(nums: inout [Int], n: Int, i: Int) {
+    var i = i
+    while true {
+        // 判断节点 i, l, r 中值最大的节点，记为 ma
+        let l = 2 * i + 1
+        let r = 2 * i + 2
+        var ma = i
+        if l < n, nums[l] > nums[ma] {
+            ma = l
+        }
+        if r < n, nums[r] > nums[ma] {
+            ma = r
+        }
+        // 若节点 i 最大或索引 l, r 越界，则无需继续堆化，跳出
+        if ma == i {
+            break
+        }
+        // 交换两节点
+        nums.swapAt(i, ma)
+        // 循环向下堆化
+        i = ma
+    }
+}
+
+/* 堆排序 */
+func heapSort(nums: inout [Int]) {
+    // 建堆操作：堆化除叶节点以外的其他所有节点
+    for i in stride(from: nums.count / 2 - 1, through: 0, by: -1) {
+        siftDown(nums: &nums, n: nums.count, i: i)
+    }
+    // 从堆中提取最大元素，循环 n-1 轮
+    for i in stride(from: nums.count - 1, to: 0, by: -1) {
+        // 交换根节点与最右叶节点（即交换首元素与尾元素）
+        nums.swapAt(0, i)
+        // 以根节点为起点，从顶至底进行堆化
+        siftDown(nums: &nums, n: i, i: 0)
+    }
+}
+
+@main
+enum HeapSort {
+    /* Driver Code */
+    static func main() {
+        var nums = [4, 1, 3, 1, 5, 2]
+        heapSort(nums: &nums)
+        print("堆排序完成后 nums = \(nums)")
+    }
+}