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

codes/rust/Cargo.toml

@@ -19,6 +19,16 @@ path = "chapter_computational_complexity/worst_best_time_complexity.rs"
 name = "space_complexity"
 path = "chapter_computational_complexity/space_complexity.rs"
 
+# Run Command: cargo run --bin iteration
+[[bin]]
+name = "iteration"
+path = "chapter_computational_complexity/iteration.rs"
+
+# Run Command: cargo run --bin recursion
+[[bin]]
+name = "recursion"
+path = "chapter_computational_complexity/recursion.rs"
+
 # Run Command: cargo run --bin two_sum
 [[bin]]
 name = "two_sum"

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}");
+}

codes/rust/chapter_computational_complexity/recursion.rs

@@ -0,0 +1,55 @@
+/*
+ * File: recursion.rs
+ * Created Time: 2023-09-02
+ * Author: night-cruise (2586447362@qq.com)
+ */
+
+
+/* 递归 */
+fn recur(n: i32) -> i32 {
+    // 终止条件
+    if n == 1 {
+        return 1;
+    }
+    // 递：递归调用
+    let res = recur(n - 1);
+    // 归：返回结果
+    n + res
+}
+
+/* 尾递归 */
+fn tail_recur(n: i32, res: i32) -> i32 {
+    // 终止条件
+    if n == 0 {
+        return res;
+    }
+    // 尾递归调用
+    tail_recur(n - 1, res + n)
+}
+
+/* 斐波那契数列：递归 */
+fn fib(n: i32) -> i32 {
+    // 终止条件 f(1) = 0, f(2) = 1
+    if n == 1 || n == 2 {
+        return n - 1;
+    }
+    // 递归调用 f(n) = f(n-1) + f(n-2)
+    let res = fib(n - 1) + fib(n - 2);
+    // 返回结果
+    res
+}
+
+/* Driver Code */
+fn main() {
+    let n = 5;
+    let mut res;
+
+    res = recur(n);
+    println!("\n递归函数的求和结果 res = {res}");
+
+    res = tail_recur(n, 0);
+    println!("\n尾递归函数的求和结果 res = {res}");
+    
+    res = fib(n);
+    println!("\n斐波那契数列的第 {n} 项为 {res}");
+}

codes/rust/chapter_tree/binary_search_tree.rs

@@ -76,7 +76,7 @@ impl BinarySearchTree {
     pub fn insert(&mut self, num: i32) {
         // 若树为空，则初始化根节点
         if self.root.is_none() {
-            self.root = TreeNode::new(num);
+            self.root = Some(TreeNode::new(num));
             return;
         }
         let mut cur = self.root.clone();