Add multilingual exercise code (#1959)

Replace the exercise pages' Python-only snippets with source-backed implementations for the 13 visible programming languages, and localize reader-facing comments by site language. Zig remains out of scope.

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codes/swift/Package.swift

@@ -11,6 +11,7 @@ let package = Package(
         .executable(name: "time_complexity", targets: ["time_complexity"]),
         .executable(name: "worst_best_time_complexity", targets: ["worst_best_time_complexity"]),
         .executable(name: "space_complexity", targets: ["space_complexity"]),
+        .executable(name: "complexity_exercises", targets: ["complexity_exercises"]),
         // chapter_array_and_linkedlist
         .executable(name: "array", targets: ["array"]),
         .executable(name: "linked_list", targets: ["linked_list"]),
@@ -70,6 +71,7 @@ let package = Package(
         .executable(name: "binary_search_recur", targets: ["binary_search_recur"]),
         .executable(name: "build_tree", targets: ["build_tree"]),
         .executable(name: "hanota", targets: ["hanota"]),
+        .executable(name: "fast_power", targets: ["fast_power"]),
         // chapter_backtracking
         .executable(name: "preorder_traversal_i_compact", targets: ["preorder_traversal_i_compact"]),
         .executable(name: "preorder_traversal_ii_compact", targets: ["preorder_traversal_ii_compact"]),
@@ -114,6 +116,7 @@ let package = Package(
         .executableTarget(name: "time_complexity", path: "chapter_computational_complexity", sources: ["time_complexity.swift"]),
         .executableTarget(name: "worst_best_time_complexity", path: "chapter_computational_complexity", sources: ["worst_best_time_complexity.swift"]),
         .executableTarget(name: "space_complexity", dependencies: ["utils"], path: "chapter_computational_complexity", sources: ["space_complexity.swift"]),
+        .executableTarget(name: "complexity_exercises", path: "chapter_computational_complexity", sources: ["complexity_exercises.swift"]),
         // chapter_array_and_linkedlist
         .executableTarget(name: "array", path: "chapter_array_and_linkedlist", sources: ["array.swift"]),
         .executableTarget(name: "linked_list", dependencies: ["utils"], path: "chapter_array_and_linkedlist", sources: ["linked_list.swift"]),
@@ -173,6 +176,7 @@ let package = Package(
         .executableTarget(name: "binary_search_recur", path: "chapter_divide_and_conquer", sources: ["binary_search_recur.swift"]),
         .executableTarget(name: "build_tree", dependencies: ["utils"], path: "chapter_divide_and_conquer", sources: ["build_tree.swift"]),
         .executableTarget(name: "hanota", path: "chapter_divide_and_conquer", sources: ["hanota.swift"]),
+        .executableTarget(name: "fast_power", path: "chapter_divide_and_conquer", sources: ["fast_power.swift"]),
         // chapter_backtracking
         .executableTarget(name: "preorder_traversal_i_compact", dependencies: ["utils"], path: "chapter_backtracking", sources: ["preorder_traversal_i_compact.swift"]),
         .executableTarget(name: "preorder_traversal_ii_compact", dependencies: ["utils"], path: "chapter_backtracking", sources: ["preorder_traversal_ii_compact.swift"]),

codes/swift/chapter_computational_complexity/complexity_exercises.swift

@@ -0,0 +1,62 @@
+/**
+ File: complexity_exercises.swift
+ Created Time: 2026-08-18
+ Author: Hello Algo Team
+ */
+
+/* 迭代求和 */
+func sumIter(n: Int) -> Int {
+    var res = 0
+    for i in 1 ... n {
+        res += i
+    }
+    return res
+}
+
+/* 递归求和 */
+func sumRecur(n: Int) -> Int {
+    if n == 1 {
+        return 1
+    }
+    return n + sumRecur(n: n - 1)
+}
+
+/* 线性阶循环 */
+func linearLoop(n: Int) -> Int {
+    var res = 0
+    for i in 0 ..< n {
+        res += i
+    }
+    return res
+}
+
+/* 平方阶循环 */
+func quadraticLoop(n: Int) -> Int {
+    var res = 0
+    for i in 0 ..< n {
+        for j in i ..< n {
+            res += j
+        }
+    }
+    return res
+}
+
+/* 对数阶循环 */
+func logarithmicLoop(n: Int) -> Int {
+    var n = n
+    while n > 1 {
+        n /= 2
+    }
+    return n
+}
+
+@main
+enum ComplexityExercises {
+    static func main() {
+        assert(sumIter(n: 1) == 1 && sumRecur(n: 1) == 1)
+        assert(sumIter(n: 4) == 10 && sumRecur(n: 4) == 10)
+        assert(linearLoop(n: 4) == 6)
+        assert(quadraticLoop(n: 4) == 20)
+        assert(logarithmicLoop(n: 4) == 1 && logarithmicLoop(n: 5) == 1)
+    }
+}

codes/swift/chapter_divide_and_conquer/fast_power.swift

@@ -0,0 +1,26 @@
+/**
+ File: fast_power.swift
+ Created Time: 2026-08-18
+ Author: Hello Algo Team
+ */
+
+/* 快速幂 */
+func fastPow(x: Int, n: Int) -> Int {
+    if n == 0 {
+        return 1
+    }
+    let half = fastPow(x: x, n: n / 2)
+    if n % 2 == 0 {
+        return half * half
+    }
+    return half * half * x
+}
+
+@main
+enum FastPower {
+    static func main() {
+        assert(fastPow(x: 7, n: 0) == 1)
+        assert(fastPow(x: 3, n: 5) == 243)
+        assert(fastPow(x: 2, n: 6) == 64)
+    }
+}