feat: add Swift codes for chapter_sorting articles (#313)

* feat: add Swift codes for bubble_sort article

* feat: add Swift codes for insertion_sort article

* feat: add Swift codes for quick_sort article

* feat: add Swift codes for merge_sort article

* feat: add Swift codes for radix_sort

* refactor: remove ^ operator

codes/swift/Package.swift

@@ -31,6 +31,11 @@ let package = Package(
         .executable(name: "linear_search", targets: ["linear_search"]),
         .executable(name: "binary_search", targets: ["binary_search"]),
         .executable(name: "hashing_search", targets: ["hashing_search"]),
+        .executable(name: "bubble_sort", targets: ["bubble_sort"]),
+        .executable(name: "insertion_sort", targets: ["insertion_sort"]),
+        .executable(name: "quick_sort", targets: ["quick_sort"]),
+        .executable(name: "merge_sort", targets: ["merge_sort"]),
+        .executable(name: "radix_sort", targets: ["radix_sort"]),
     ],
     targets: [
         .target(name: "utils", path: "utils"),
@@ -60,5 +65,10 @@ let package = Package(
         .executableTarget(name: "linear_search", dependencies: ["utils"], path: "chapter_searching", sources: ["linear_search.swift"]),
         .executableTarget(name: "binary_search", path: "chapter_searching", sources: ["binary_search.swift"]),
         .executableTarget(name: "hashing_search", dependencies: ["utils"], path: "chapter_searching", sources: ["hashing_search.swift"]),
+        .executableTarget(name: "bubble_sort", path: "chapter_sorting", sources: ["bubble_sort.swift"]),
+        .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: "radix_sort", path: "chapter_sorting", sources: ["radix_sort.swift"]),
     ]
 )

codes/swift/chapter_sorting/bubble_sort.swift

@@ -0,0 +1,55 @@
+/**
+ * File: bubble_sort.swift
+ * Created Time: 2023-01-29
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+/* 冒泡排序 */
+func bubbleSort(nums: inout [Int]) {
+    // 外循环：待排序元素数量为 n-1, n-2, ..., 1
+    for i in stride(from: nums.count - 1, to: 0, by: -1) {
+        // 内循环：冒泡操作
+        for j in stride(from: 0, to: i, by: 1) {
+            if nums[j] > nums[j + 1] {
+                // 交换 nums[j] 与 nums[j + 1]
+                let tmp = nums[j]
+                nums[j] = nums[j + 1]
+                nums[j + 1] = tmp
+            }
+        }
+    }
+}
+
+/* 冒泡排序（标志优化）*/
+func bubbleSortWithFlag(nums: inout [Int]) {
+    // 外循环：待排序元素数量为 n-1, n-2, ..., 1
+    for i in stride(from: nums.count - 1, to: 0, by: -1) {
+        var flag = false // 初始化标志位
+        for j in stride(from: 0, to: i, by: 1) {
+            if nums[j] > nums[j + 1] {
+                // 交换 nums[j] 与 nums[j + 1]
+                let tmp = nums[j]
+                nums[j] = nums[j + 1]
+                nums[j + 1] = tmp
+                flag = true // 记录交换元素
+            }
+        }
+        if !flag { // 此轮冒泡未交换任何元素，直接跳出
+            break
+        }
+    }
+}
+
+@main
+enum BubbleSort {
+    /* Driver Code */
+    static func main() {
+        var nums = [4, 1, 3, 1, 5, 2]
+        bubbleSort(nums: &nums)
+        print("冒泡排序完成后 nums = \(nums)")
+
+        var nums1 = [4, 1, 3, 1, 5, 2]
+        bubbleSortWithFlag(nums: &nums1)
+        print("冒泡排序完成后 nums1 = \(nums1)")
+    }
+}

codes/swift/chapter_sorting/insertion_sort.swift

@@ -0,0 +1,30 @@
+/**
+ * File: insertion_sort.swift
+ * Created Time: 2023-01-29
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+/* 插入排序 */
+func insertionSort(nums: inout [Int]) {
+    // 外循环：base = nums[1], nums[2], ..., nums[n-1]
+    for i in stride(from: 1, to: nums.count, by: 1) {
+        let base = nums[i]
+        var j = i - 1
+        // 内循环：将 base 插入到左边的正确位置
+        while j >= 0, nums[j] > base {
+            nums[j + 1] = nums[j] // 1. 将 nums[j] 向右移动一位
+            j -= 1
+        }
+        nums[j + 1] = base // 2. 将 base 赋值到正确位置
+    }
+}
+
+@main
+enum InsertionSort {
+    /* Driver Code */
+    static func main() {
+        var nums = [4, 1, 3, 1, 5, 2]
+        insertionSort(nums: &nums)
+        print("插入排序完成后 nums = \(nums)")
+    }
+}

codes/swift/chapter_sorting/merge_sort.swift

@@ -0,0 +1,67 @@
+/**
+ * File: merge_sort.swift
+ * Created Time: 2023-01-29
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+/**
+ * 合并左子数组和右子数组
+ * 左子数组区间 [left, mid]
+ * 右子数组区间 [mid + 1, right]
+ */
+func merge(nums: inout [Int], left: Int, mid: Int, right: Int) {
+    // 初始化辅助数组
+    let tmp = Array(nums[left ..< (right + 1)])
+    // 左子数组的起始索引和结束索引
+    let leftStart = left - left
+    let leftEnd = mid - left
+    // 右子数组的起始索引和结束索引
+    let rightStart = mid + 1 - left
+    let rightEnd = right - left
+    // i, j 分别指向左子数组、右子数组的首元素
+    var i = leftStart
+    var j = rightStart
+    // 通过覆盖原数组 nums 来合并左子数组和右子数组
+    for k in left ... right {
+        // 若“左子数组已全部合并完”，则选取右子数组元素，并且 j++
+        if i > leftEnd {
+            nums[k] = tmp[j]
+            j += 1
+        }
+        // 否则，若“右子数组已全部合并完”或“左子数组元素 <= 右子数组元素”，则选取左子数组元素，并且 i++
+        else if j > rightEnd || tmp[i] <= tmp[j] {
+            nums[k] = tmp[i]
+            i += 1
+        }
+        // 否则，若“左右子数组都未全部合并完”且“左子数组元素 > 右子数组元素”，则选取右子数组元素，并且 j++
+        else {
+            nums[k] = tmp[j]
+            j += 1
+        }
+    }
+}
+
+/* 归并排序 */
+func mergeSort(nums: inout [Int], left: Int, right: Int) {
+    // 终止条件
+    if left >= right { // 当子数组长度为 1 时终止递归
+        return
+    }
+    // 划分阶段
+    let mid = (left + right) / 2 // 计算中点
+    mergeSort(nums: &nums, left: left, right: mid) // 递归左子数组
+    mergeSort(nums: &nums, left: mid + 1, right: right) // 递归右子数组
+    // 合并阶段
+    merge(nums: &nums, left: left, mid: mid, right: right)
+}
+
+@main
+enum MergeSort {
+    /* Driver Code */
+    static func main() {
+        /* 归并排序 */
+        var nums = [7, 3, 2, 6, 0, 1, 5, 4]
+        mergeSort(nums: &nums, left: 0, right: nums.count - 1)
+        print("归并排序完成后 nums = \(nums)")
+    }
+}

codes/swift/chapter_sorting/quick_sort.swift

@@ -0,0 +1,124 @@
+/**
+ * File: quick_sort.swift
+ * Created Time: 2023-01-29
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+/* 元素交换 */
+func swap(nums: inout [Int], i: Int, j: Int) {
+    let tmp = nums[i]
+    nums[i] = nums[j]
+    nums[j] = tmp
+}
+
+/* 快速排序类 */
+// 快速排序类-哨兵划分
+func quickSortPartition(nums: inout [Int], left: Int, right: Int) -> Int {
+    // 以 nums[left] 作为基准数
+    var i = left
+    var j = right
+    while i < j {
+        while i < j, nums[j] >= nums[left] {
+            j -= 1 // 从右向左找首个小于基准数的元素
+        }
+        while i < j, nums[i] <= nums[left] {
+            i += 1 // 从左向右找首个大于基准数的元素
+        }
+        swap(nums: &nums, i: i, j: j) // 交换这两个元素
+    }
+    swap(nums: &nums, i: i, j: left) // 将基准数交换至两子数组的分界线
+    return i // 返回基准数的索引
+}
+
+// 快速排序类-快速排序
+func quickSort(nums: inout [Int], left: Int, right: Int) {
+    // 子数组长度为 1 时终止递归
+    if left >= right {
+        return
+    }
+    // 哨兵划分
+    let pivot = quickSortPartition(nums: &nums, left: left, right: right)
+    // 递归左子数组、右子数组
+    quickSort(nums: &nums, left: left, right: pivot - 1)
+    quickSort(nums: &nums, left: pivot + 1, right: right)
+}
+
+/* 快速排序类（中位基准数优化） */
+// 快速排序类（中位基准数优化）-选取三个元素的中位数
+func quickSortMedianThree(nums: [Int], left: Int, mid: Int, right: Int) -> Int {
+    if (nums[left] < nums[mid]) != (nums[left] < nums[right]) {
+        return left
+    } else if (nums[mid] < nums[left]) != (nums[mid] < nums[right]) {
+        return mid
+    } else {
+        return right
+    }
+}
+
+// 快速排序类（中位基准数优化）-哨兵划分（三数取中值）
+func quickSortMedianPartition(nums: inout [Int], left: Int, right: Int) -> Int {
+    // 选取三个候选元素的中位数
+    let med = quickSortMedianThree(nums: nums, left: left, mid: (left + right) / 2, right: right)
+    // 将中位数交换至数组最左端
+    swap(nums: &nums, i: left, j: med)
+    return quickSortPartition(nums: &nums, left: left, right: right)
+}
+
+// 快速排序类（中位基准数优化）-快速排序
+func quickSortMedian(nums: inout [Int], left: Int, right: Int) {
+    // 子数组长度为 1 时终止递归
+    if left >= right {
+        return
+    }
+    // 哨兵划分
+    let pivot = quickSortMedianPartition(nums: &nums, left: left, right: right)
+    // 递归左子数组、右子数组
+    quickSortMedian(nums: &nums, left: left, right: pivot - 1)
+    quickSortMedian(nums: &nums, left: pivot + 1, right: right)
+}
+
+/* 快速排序类（尾递归优化） */
+// 快速排序类（尾递归优化）-哨兵划分
+func quickSortTailCallPartition(nums: inout [Int], left: Int, right: Int) -> Int {
+    quickSortPartition(nums: &nums, left: left, right: right)
+}
+
+// 快速排序类（尾递归优化）-快速排序（尾递归优化）
+func quickSortTailCall(nums: inout [Int], left: Int, right: Int) {
+    var left = left
+    var right = right
+    // 子数组长度为 1 时终止
+    while left < right {
+        // 哨兵划分操作
+        let pivot = quickSortTailCallPartition(nums: &nums, left: left, right: right)
+        // 对两个子数组中较短的那个执行快排
+        if (pivot - left) < (right - pivot) {
+            quickSortTailCall(nums: &nums, left: left, right: pivot - 1) // 递归排序左子数组
+            left = pivot + 1 // 剩余待排序区间为 [pivot + 1, right]
+        } else {
+            quickSortTailCall(nums: &nums, left: pivot + 1, right: right) // 递归排序右子数组
+            right = pivot - 1 // 剩余待排序区间为 [left, pivot - 1]
+        }
+    }
+}
+
+@main
+enum QuickSort {
+    /* Driver Code */
+    static func main() {
+        /* 快速排序 */
+        var nums = [2, 4, 1, 0, 3, 5]
+        quickSort(nums: &nums, left: 0, right: nums.count - 1)
+        print("快速排序完成后 nums = \(nums)")
+
+        /* 快速排序（中位基准数优化） */
+        var nums1 = [2, 4, 1, 0, 3, 5]
+        quickSortMedian(nums: &nums1, left: 0, right: nums1.count - 1)
+        print("快速排序（中位基准数优化）完成后 nums1 = \(nums1)")
+
+        /* 快速排序（尾递归优化） */
+        var nums2 = [2, 4, 1, 0, 3, 5]
+        quickSortTailCall(nums: &nums2, left: 0, right: nums2.count - 1)
+        print("快速排序（尾递归优化）完成后 nums2 = \(nums2)")
+    }
+}

codes/swift/chapter_sorting/radix_sort.swift

@@ -0,0 +1,70 @@
+/**
+ * File: radix_sort.swift
+ * Created Time: 2023-01-29
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+/* 获取元素 num 的第 k 位，其中 exp = 10^(k-1) */
+func digit(num: Int, exp: Int) -> Int {
+    // 传入 exp 而非 k 可以避免在此重复执行昂贵的次方计算
+    (num / exp) % 10
+}
+
+/* 计数排序（根据 nums 第 k 位排序） */
+func countSort(nums: inout [Int], exp: Int) {
+    // 十进制的各位数字范围为 0~9 ，因此需要长度为 10 的桶
+    var bucket = Array(repeating: 0, count: 10)
+    let n = nums.count
+    // 借助桶来统计 0~9 各数字的出现次数
+    for i in nums.indices {
+        let d = digit(num: nums[i], exp: exp) // 获取 nums[i] 第 k 位，记为 d
+        bucket[d] += 1 // 统计数字 d 的出现次数
+    }
+    // 求前缀和，将“出现个数”转换为“数组索引”
+    for i in 1 ..< 10 {
+        bucket[i] += bucket[i - 1]
+    }
+    // 倒序遍历，根据桶内统计结果，将各元素填入暂存数组 tmp
+    var tmp = Array(repeating: 0, count: n)
+    for i in stride(from: n - 1, through: 0, by: -1) {
+        let d = digit(num: nums[i], exp: exp)
+        let j = bucket[d] - 1 // 获取 d 在数组中的索引 j
+        tmp[j] = nums[i] // 将当前元素填入索引 j
+        bucket[d] -= 1 // 将 d 的数量减 1
+    }
+    // 将 tmp 复制到 nums
+    for i in nums.indices {
+        nums[i] = tmp[i]
+    }
+}
+
+/* 基数排序 */
+func radixSort(nums: inout [Int]) {
+    // 获取数组的最大元素，用于判断最大位数
+    var ma = Int.min
+    for num in nums {
+        if num > ma {
+            ma = num
+        }
+    }
+    // 按照从低位到高位的顺序遍历
+    for exp in sequence(first: 1, next: { ma >= ($0 * 10) ? $0 * 10 : nil }) {
+        // 对数组元素的第 k 位执行「计数排序」
+        // k = 1 -> exp = 1
+        // k = 2 -> exp = 10
+        // k = 3 -> exp = 100
+        // 即 exp = 10^(k-1)
+        countSort(nums: &nums, exp: exp)
+    }
+}
+
+@main
+enum RadixSort {
+    /* Driver Code */
+    static func main() {
+        /* 基数排序 */
+        var nums = [23, 12, 3, 4, 788, 192]
+        radixSort(nums: &nums)
+        print("基数排序完成后 nums = \(nums)")
+    }
+}