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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ru/codes/cpp/chapter_computational_complexity/CMakeLists.txt

@@ -2,4 +2,5 @@ add_executable(iteration iteration.cpp)
 add_executable(recursion recursion.cpp)
 add_executable(space_complexity space_complexity.cpp)
 add_executable(time_complexity time_complexity.cpp)
-add_executable(worst_best_time_complexity worst_best_time_complexity.cpp)
+add_executable(worst_best_time_complexity worst_best_time_complexity.cpp)
+add_executable(complexity_exercises complexity_exercises.cpp)

ru/codes/cpp/chapter_computational_complexity/complexity_exercises.cpp

@@ -0,0 +1,61 @@
+/**
+ * File: complexity_exercises.cpp
+ * Created Time: 2026-08-18
+ * Author: Hello Algo Team
+ */
+
+#include <cassert>
+
+/* Итеративное суммирование */
+int sumIter(int n) {
+    int res = 0;
+    for (int i = 1; i <= n; ++i) {
+        res += i;
+    }
+    return res;
+}
+
+/* Рекурсивное суммирование */
+int sumRecur(int n) {
+    if (n == 1) {
+        return 1;
+    }
+    return n + sumRecur(n - 1);
+}
+
+/* Цикл линейной сложности */
+int linearLoop(int n) {
+    int res = 0;
+    for (int i = 0; i < n; ++i) {
+        res += i;
+    }
+    return res;
+}
+
+/* Цикл квадратичной сложности */
+int quadraticLoop(int n) {
+    int res = 0;
+    for (int i = 0; i < n; ++i) {
+        for (int j = i; j < n; ++j) {
+            res += j;
+        }
+    }
+    return res;
+}
+
+/* Цикл логарифмической сложности */
+int logarithmicLoop(int n) {
+    while (n > 1) {
+        n /= 2;
+    }
+    return n;
+}
+
+int main() {
+    assert(sumIter(1) == 1 && sumRecur(1) == 1);
+    assert(sumIter(4) == 10 && sumRecur(4) == 10);
+    assert(linearLoop(4) == 6);
+    assert(quadraticLoop(4) == 20);
+    assert(logarithmicLoop(4) == 1 && logarithmicLoop(5) == 1);
+    return 0;
+}

ru/codes/cpp/chapter_divide_and_conquer/CMakeLists.txt

@@ -1,3 +1,4 @@
 add_executable(binary_search_recur binary_search_recur.cpp)
 add_executable(build_tree build_tree.cpp)
-add_executable(hanota hanota.cpp)
+add_executable(hanota hanota.cpp)
+add_executable(fast_power fast_power.cpp)

ru/codes/cpp/chapter_divide_and_conquer/fast_power.cpp

@@ -0,0 +1,26 @@
+/**
+ * File: fast_power.cpp
+ * Created Time: 2026-08-18
+ * Author: Hello Algo Team
+ */
+
+#include <cassert>
+
+/* Быстрое возведение в степень */
+int fastPow(int x, int n) {
+    if (n == 0) {
+        return 1;
+    }
+    int half = fastPow(x, n / 2);
+    if (n % 2 == 0) {
+        return half * half;
+    }
+    return half * half * x;
+}
+
+int main() {
+    assert(fastPow(7, 0) == 1);
+    assert(fastPow(3, 5) == 243);
+    assert(fastPow(2, 6) == 64);
+    return 0;
+}