fix(Rust): no need to clone in hash put fn (#1226)

* no need to clone in hash put fn

* fmt rust code

* make code more readable

* Change vec append to extend, more friendly to rookie rust dev

* drop comment

codes/rust/chapter_hashing/hash_map_chaining.rs

@@ -102,17 +102,14 @@ impl HashMapChaining {
         // 遍历桶，若遇到指定 key ，则更新对应 val 并返回
         for pair in bucket {
             if pair.key == key {
-                pair.val = val.clone();
+                pair.val = val;
                 return;
             }
         }
         let bucket = &mut self.buckets[index];
 
         // 若无该 key ，则将键值对添加至尾部
-        let pair = Pair {
-            key,
-            val: val.clone(),
-        };
+        let pair = Pair { key, val };
         bucket.push(pair);
         self.size += 1;
     }

codes/rust/chapter_tree/binary_tree_bfs.rs

@@ -14,7 +14,7 @@ use tree_node::{vec_to_tree, TreeNode};
 fn level_order(root: &Rc<RefCell<TreeNode>>) -> Vec<i32> {
     // 初始化队列，加入根节点
     let mut que = VecDeque::new();
-    que.push_back(Rc::clone(&root));
+    que.push_back(root.clone());
     // 初始化一个列表，用于保存遍历序列
     let mut vec = Vec::new();
 
@@ -22,10 +22,10 @@ fn level_order(root: &Rc<RefCell<TreeNode>>) -> Vec<i32> {
         // 队列出队
         vec.push(node.borrow().val); // 保存节点值
         if let Some(left) = node.borrow().left.as_ref() {
-            que.push_back(Rc::clone(left)); // 左子节点入队
+            que.push_back(left.clone()); // 左子节点入队
         }
         if let Some(right) = node.borrow().right.as_ref() {
-            que.push_back(Rc::clone(right)); // 右子节点入队
+            que.push_back(right.clone()); // 右子节点入队
         };
     }
     vec

codes/rust/chapter_tree/binary_tree_dfs.rs

@@ -17,8 +17,8 @@ fn pre_order(root: Option<&Rc<RefCell<TreeNode>>>) -> Vec<i32> {
     if let Some(node) = root {
         // 访问优先级：根节点 -> 左子树 -> 右子树
         result.push(node.borrow().val);
-        result.append(&mut pre_order(node.borrow().left.as_ref()));
-        result.append(&mut pre_order(node.borrow().right.as_ref()));
+        result.extend(pre_order(node.borrow().left.as_ref()));
+        result.extend(pre_order(node.borrow().right.as_ref()));
     }
     result
 }
@@ -29,9 +29,9 @@ fn in_order(root: Option<&Rc<RefCell<TreeNode>>>) -> Vec<i32> {
 
     if let Some(node) = root {
         // 访问优先级：左子树 -> 根节点 -> 右子树
-        result.append(&mut in_order(node.borrow().left.as_ref()));
+        result.extend(in_order(node.borrow().left.as_ref()));
         result.push(node.borrow().val);
-        result.append(&mut in_order(node.borrow().right.as_ref()));
+        result.extend(in_order(node.borrow().right.as_ref()));
     }
     result
 }
@@ -42,8 +42,8 @@ fn post_order(root: Option<&Rc<RefCell<TreeNode>>>) -> Vec<i32> {
 
     if let Some(node) = root {
         // 访问优先级：左子树 -> 右子树 -> 根节点
-        result.append(&mut post_order(node.borrow().left.as_ref()));
-        result.append(&mut post_order(node.borrow().right.as_ref()));
+        result.extend(post_order(node.borrow().left.as_ref()));
+        result.extend(post_order(node.borrow().right.as_ref()));
         result.push(node.borrow().val);
     }
     result

codes/rust/include/tree_node.rs

@@ -25,7 +25,7 @@ impl TreeNode {
             height: 0,
             parent: None,
             left: None,
-            right: None
+            right: None,
         }))
     }
 }
@@ -77,7 +77,8 @@ fn tree_to_vec_dfs(root: Option<Rc<RefCell<TreeNode>>>, i: usize, res: &mut Vec<
         return;
     }
     let root = root.unwrap();
-    while i >= res.len() {
+    // i + 1 is the minimum valid size to access index i
+    while res.len() < i + 1 {
         res.push(None);
     }
     res[i] = Some(root.borrow().val);