cargo fmt rust code (#1131)

* cargo fmt code

* Add empty line to seperate unrelated comments

* Fix review

* Update bubble_sort.rs

* Update merge_sort.rs

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/rust/chapter_dynamic_programming/climbing_stairs_backtrack.rs

@@ -1,37 +1,41 @@
-/*
- * File: climbing_stairs_backtrack.rs
- * Created Time: 2023-07-09
- * Author: codingonion (coderonion@gmail.com)
- */
-
-/* 回溯 */
-fn backtrack(choices: &[i32], state: i32, n: i32, res: &mut [i32]) {
-    // 当爬到第 n 阶时，方案数量加 1
-    if state == n { res[0] = res[0] + 1; }
-    // 遍历所有选择
-    for &choice in choices {
-        // 剪枝：不允许越过第 n 阶
-        if state + choice > n { continue; }
-        // 尝试：做出选择，更新状态
-        backtrack(choices, state + choice, n, res);
-        // 回退
-    }
-}
-
-/* 爬楼梯：回溯 */
-fn climbing_stairs_backtrack(n: usize) -> i32 {
-    let choices = vec![ 1, 2 ]; // 可选择向上爬 1 阶或 2 阶
-    let state = 0; // 从第 0 阶开始爬
-    let mut res = Vec::new();
-    res.push(0); // 使用 res[0] 记录方案数量
-    backtrack(&choices, state, n as i32, &mut res);
-    res[0]
-}
-
-/* Driver Code */
-pub fn main() {
-    let n: usize = 9;
-
-    let res = climbing_stairs_backtrack(n);
-    println!("爬 {n} 阶楼梯共有 {res} 种方案");
-}
+/*
+ * File: climbing_stairs_backtrack.rs
+ * Created Time: 2023-07-09
+ * Author: codingonion (coderonion@gmail.com)
+ */
+
+/* 回溯 */
+fn backtrack(choices: &[i32], state: i32, n: i32, res: &mut [i32]) {
+    // 当爬到第 n 阶时，方案数量加 1
+    if state == n {
+        res[0] = res[0] + 1;
+    }
+    // 遍历所有选择
+    for &choice in choices {
+        // 剪枝：不允许越过第 n 阶
+        if state + choice > n {
+            continue;
+        }
+        // 尝试：做出选择，更新状态
+        backtrack(choices, state + choice, n, res);
+        // 回退
+    }
+}
+
+/* 爬楼梯：回溯 */
+fn climbing_stairs_backtrack(n: usize) -> i32 {
+    let choices = vec![1, 2]; // 可选择向上爬 1 阶或 2 阶
+    let state = 0; // 从第 0 阶开始爬
+    let mut res = Vec::new();
+    res.push(0); // 使用 res[0] 记录方案数量
+    backtrack(&choices, state, n as i32, &mut res);
+    res[0]
+}
+
+/* Driver Code */
+pub fn main() {
+    let n: usize = 9;
+
+    let res = climbing_stairs_backtrack(n);
+    println!("爬 {n} 阶楼梯共有 {res} 种方案");
+}