feat: add rust codes for chapter computational complexity (#714)

codes/rust/chapter_computational_complexity/iteration.rs

@@ -0,0 +1,73 @@
+/*
+ * File: iteration.rs
+ * Created Time: 2023-09-02
+ * Author: night-cruise (2586447362@qq.com)
+ */
+
+ 
+/*  for 循环 */
+fn for_loop(n: i32) -> i32 {
+    let mut res = 0;
+    // 循环求和 1, 2, ..., n-1, n
+    for i in 1..=n {
+        res += i;
+    }
+    res
+} 
+
+/* while 循环 */
+fn while_loop(n: i32) -> i32 {
+    let mut res = 0;
+    let mut i = 1; // 初始化条件变量
+    // 循环求和 1, 2, ..., n-1, n
+    while i <= n {
+        res += i;
+        i += 1; // 更新条件变量
+    }
+    res
+}
+
+/* while 循环（两次更新） */
+fn while_loop_ii(n: i32) -> i32 {
+    let mut res = 0;
+    let mut i = 1; // 初始化条件变量
+    // 循环求和 1, 4, ...
+    while i <= n {
+        res += i;
+        // 更新条件变量
+        i += 1;
+        i *= 2;
+    }
+    res
+}
+
+/* 双层 for 循环 */
+fn nested_for_loop(n: i32) -> String {
+    let mut res = vec![];
+    // 循环 i = 1, 2, ..., n-1, n
+    for i in 1..=n {
+        // 循环 j = 1, 2, ..., n-1, n
+        for j in 1..=n {
+            res.push(format!("({}, {}), ", i, j));
+        }
+    }
+    res.join("")
+}
+ 
+/* Driver Code */
+fn main() {
+    let n = 5;
+    let mut res;
+
+    res = for_loop(n);
+    println!("\nfor 循环的求和结果 res = {res}");
+
+    res = while_loop(n);
+    println!("\nwhile 循环的求和结果 res = {res}");
+
+    res = while_loop_ii(n);
+    println!("\nwhile 循环（两次更新）求和结果 res = {}", res);
+
+    let res = nested_for_loop(n);
+    println!("\n双层 for 循环的遍历结果 {res}");
+}