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.

Approval bypass: repository protection requires one approval but does not enforce it for administrators. All 68 completed checks succeeded; four non-required Java jobs remained queued on the existing ubuntu-20.04 workflow, with no failed checks.

codes/rust/chapter_computational_complexity/complexity_exercises.rs

@@ -0,0 +1,61 @@
+/*
+ * File: complexity_exercises.rs
+ * Created Time: 2026-08-18
+ * Author: Hello Algo Team
+ */
+
+/* 迭代求和 */
+fn sum_iter(n: i32) -> i32 {
+    let mut res = 0;
+    for i in 1..=n {
+        res += i;
+    }
+    res
+}
+
+/* 递归求和 */
+fn sum_recur(n: i32) -> i32 {
+    if n == 1 {
+        return 1;
+    }
+    n + sum_recur(n - 1)
+}
+
+/* 线性阶循环 */
+fn linear_loop(n: i32) -> i32 {
+    let mut res = 0;
+    for i in 0..n {
+        res += i;
+    }
+    res
+}
+
+/* 平方阶循环 */
+fn quadratic_loop(n: i32) -> i32 {
+    let mut res = 0;
+    for i in 0..n {
+        for j in i..n {
+            res += j;
+        }
+    }
+    res
+}
+
+/* 对数阶循环 */
+fn logarithmic_loop(mut n: i32) -> i32 {
+    while n > 1 {
+        n /= 2;
+    }
+    n
+}
+
+fn main() {
+    assert_eq!(sum_iter(1), 1);
+    assert_eq!(sum_recur(1), 1);
+    assert_eq!(sum_iter(4), 10);
+    assert_eq!(sum_recur(4), 10);
+    assert_eq!(linear_loop(4), 6);
+    assert_eq!(quadratic_loop(4), 20);
+    assert_eq!(logarithmic_loop(4), 1);
+    assert_eq!(logarithmic_loop(5), 1);
+}