From 3af00d00d7ba1c2ce5a07036fc397f203b0355f5 Mon Sep 17 00:00:00 2001
From: Night Cruising <77157236+night-cruise@users.noreply.github.com>
Date: Sat, 2 Sep 2023 16:08:52 +0800
Subject: [PATCH] feat: add rust codes for chapter computational complexity
 (#714)

---
 codes/rust/Cargo.toml                         | 10 +++
 .../iteration.rs                              | 73 +++++++++++++++++++
 .../recursion.rs                              | 55 ++++++++++++++
 codes/rust/chapter_tree/binary_search_tree.rs |  2 +-
 4 files changed, 139 insertions(+), 1 deletion(-)
 create mode 100644 codes/rust/chapter_computational_complexity/iteration.rs
 create mode 100644 codes/rust/chapter_computational_complexity/recursion.rs

diff --git a/codes/rust/Cargo.toml b/codes/rust/Cargo.toml
index c2978fde0..3db952084 100644
--- a/codes/rust/Cargo.toml
+++ b/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"
diff --git a/codes/rust/chapter_computational_complexity/iteration.rs b/codes/rust/chapter_computational_complexity/iteration.rs
new file mode 100644
index 000000000..7f2b7d936
--- /dev/null
+++ b/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}");
+}
\ No newline at end of file
diff --git a/codes/rust/chapter_computational_complexity/recursion.rs b/codes/rust/chapter_computational_complexity/recursion.rs
new file mode 100644
index 000000000..d8c2a8d7f
--- /dev/null
+++ b/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}");
+}
\ No newline at end of file
diff --git a/codes/rust/chapter_tree/binary_search_tree.rs b/codes/rust/chapter_tree/binary_search_tree.rs
index 1ed22a3e0..e6a1e7dd6 100644
--- a/codes/rust/chapter_tree/binary_search_tree.rs
+++ b/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();