diff --git a/codes/cpp/chapter_divide_and_conquer/build_tree.cpp b/codes/cpp/chapter_divide_and_conquer/build_tree.cpp
index 51b8fbe24..d35009d90 100644
--- a/codes/cpp/chapter_divide_and_conquer/build_tree.cpp
+++ b/codes/cpp/chapter_divide_and_conquer/build_tree.cpp
@@ -7,18 +7,18 @@
 #include "../utils/common.hpp"
 
 /* 构建二叉树：分治 */
-TreeNode *dfs(vector<int> &preorder, vector<int> &inorder, unordered_map<int, int> &hmap, int i, int l, int r) {
+TreeNode *dfs(vector<int> &preorder, unordered_map<int, int> &inorderMap, int i, int l, int r) {
     // 子树区间为空时终止
     if (r - l < 0)
         return NULL;
     // 初始化根节点
     TreeNode *root = new TreeNode(preorder[i]);
     // 查询 m ，从而划分左右子树
-    int m = hmap[preorder[i]];
+    int m = inorderMap[preorder[i]];
     // 子问题：构建左子树
-    root->left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
+    root->left = dfs(preorder, inorderMap, i + 1, l, m - 1);
     // 子问题：构建右子树
-    root->right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
+    root->right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
     // 返回根节点
     return root;
 }
@@ -26,11 +26,11 @@ TreeNode *dfs(vector<int> &preorder, vector<int> &inorder, unordered_map<int, in
 /* 构建二叉树 */
 TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
     // 初始化哈希表，存储 inorder 元素到索引的映射
-    unordered_map<int, int> hmap;
+    unordered_map<int, int> inorderMap;
     for (int i = 0; i < inorder.size(); i++) {
-        hmap[inorder[i]] = i;
+        inorderMap[inorder[i]] = i;
     }
-    TreeNode *root = dfs(preorder, inorder, hmap, 0, 0, inorder.size() - 1);
+    TreeNode *root = dfs(preorder, inorderMap, 0, 0, inorder.size() - 1);
     return root;
 }
 
diff --git a/codes/csharp/chapter_divide_and_conquer/build_tree.cs b/codes/csharp/chapter_divide_and_conquer/build_tree.cs
index 104a4b55b..dcd091f0a 100644
--- a/codes/csharp/chapter_divide_and_conquer/build_tree.cs
+++ b/codes/csharp/chapter_divide_and_conquer/build_tree.cs
@@ -8,18 +8,18 @@ namespace hello_algo.chapter_divide_and_conquer;
 
 public class build_tree {
     /* 构建二叉树：分治 */
-    public TreeNode dfs(int[] preorder, int[] inorder, Dictionary<int, int> hmap, int i, int l, int r) {
+    public TreeNode dfs(int[] preorder, Dictionary<int, int> inorderMap, int i, int l, int r) {
         // 子树区间为空时终止
         if (r - l < 0)
             return null;
         // 初始化根节点
         TreeNode root = new TreeNode(preorder[i]);
         // 查询 m ，从而划分左右子树
-        int m = hmap[preorder[i]];
+        int m = inorderMap[preorder[i]];
         // 子问题：构建左子树
-        root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
+        root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
         // 子问题：构建右子树
-        root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
+        root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
         // 返回根节点
         return root;
     }
@@ -27,11 +27,11 @@ public class build_tree {
     /* 构建二叉树 */
     public TreeNode buildTree(int[] preorder, int[] inorder) {
         // 初始化哈希表，存储 inorder 元素到索引的映射
-        Dictionary<int, int> hmap = new Dictionary<int, int>();
+        Dictionary<int, int> inorderMap = new Dictionary<int, int>();
         for (int i = 0; i < inorder.Length; i++) {
-            hmap.TryAdd(inorder[i], i);
+            inorderMap.TryAdd(inorder[i], i);
         }
-        TreeNode root = dfs(preorder, inorder, hmap, 0, 0, inorder.Length - 1);
+        TreeNode root = dfs(preorder, inorderMap, 0, 0, inorder.Length - 1);
         return root;
     }
 
diff --git a/codes/csharp/chapter_tree/binary_search_tree.cs b/codes/csharp/chapter_tree/binary_search_tree.cs
index a88dd3bf3..2b85da325 100644
--- a/codes/csharp/chapter_tree/binary_search_tree.cs
+++ b/codes/csharp/chapter_tree/binary_search_tree.cs
@@ -91,7 +91,7 @@ class BinarySearchTree {
                 cur = cur.left;
         }
         // 若无待删除节点，则直接返回
-        if (cur == null || pre == null)
+        if (cur == null)
             return;
         // 子节点数量 = 0 or 1
         if (cur.left == null || cur.right == null) {
diff --git a/codes/dart/chapter_divide_and_conquer/build_tree.dart b/codes/dart/chapter_divide_and_conquer/build_tree.dart
index 5c7c0662c..f31cd0906 100644
--- a/codes/dart/chapter_divide_and_conquer/build_tree.dart
+++ b/codes/dart/chapter_divide_and_conquer/build_tree.dart
@@ -10,8 +10,7 @@ import '../utils/tree_node.dart';
 /* 构建二叉树：分治 */
 TreeNode? dfs(
   List<int> preorder,
-  List<int> inorder,
-  Map<int, int> hmap,
+  Map<int, int> inorderMap,
   int i,
   int l,
   int r,
@@ -23,11 +22,11 @@ TreeNode? dfs(
   // 初始化根节点
   TreeNode? root = TreeNode(preorder[i]);
   // 查询 m ，从而划分左右子树
-  int m = hmap[preorder[i]]!;
+  int m = inorderMap[preorder[i]]!;
   // 子问题：构建左子树
-  root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
+  root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
   // 子问题：构建右子树
-  root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
+  root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
   // 返回根节点
   return root;
 }
@@ -35,11 +34,11 @@ TreeNode? dfs(
 /* 构建二叉树 */
 TreeNode? buildTree(List<int> preorder, List<int> inorder) {
   // 初始化哈希表，存储 inorder 元素到索引的映射
-  Map<int, int> hmap = {};
+  Map<int, int> inorderMap = {};
   for (int i = 0; i < inorder.length; i++) {
-    hmap[inorder[i]] = i;
+    inorderMap[inorder[i]] = i;
   }
-  TreeNode? root = dfs(preorder, inorder, hmap, 0, 0, inorder.length - 1);
+  TreeNode? root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
   return root;
 }
 
diff --git a/codes/go/chapter_divide_and_conquer/build_tree.go b/codes/go/chapter_divide_and_conquer/build_tree.go
index 6e8818052..625040f7e 100644
--- a/codes/go/chapter_divide_and_conquer/build_tree.go
+++ b/codes/go/chapter_divide_and_conquer/build_tree.go
@@ -7,7 +7,7 @@ package chapter_divide_and_conquer
 import . "github.com/krahets/hello-algo/pkg"
 
 /* 构建二叉树：分治 */
-func dfsBuildTree(preorder, inorder []int, hmap map[int]int, i, l, r int) *TreeNode {
+func dfsBuildTree(preorder []int, inorderMap map[int]int, i, l, r int) *TreeNode {
 	// 子树区间为空时终止
 	if r-l < 0 {
 		return nil
@@ -15,11 +15,11 @@ func dfsBuildTree(preorder, inorder []int, hmap map[int]int, i, l, r int) *TreeN
 	// 初始化根节点
 	root := NewTreeNode(preorder[i])
 	// 查询 m ，从而划分左右子树
-	m := hmap[preorder[i]]
+	m := inorderMap[preorder[i]]
 	// 子问题：构建左子树
-	root.Left = dfsBuildTree(preorder, inorder, hmap, i+1, l, m-1)
+	root.Left = dfsBuildTree(preorder, inorderMap, i+1, l, m-1)
 	// 子问题：构建右子树
-	root.Right = dfsBuildTree(preorder, inorder, hmap, i+1+m-l, m+1, r)
+	root.Right = dfsBuildTree(preorder, inorderMap, i+1+m-l, m+1, r)
 	// 返回根节点
 	return root
 }
@@ -27,11 +27,11 @@ func dfsBuildTree(preorder, inorder []int, hmap map[int]int, i, l, r int) *TreeN
 /* 构建二叉树 */
 func buildTree(preorder, inorder []int) *TreeNode {
 	// 初始化哈希表，存储 inorder 元素到索引的映射
-	hmap := make(map[int]int, len(inorder))
+	inorderMap := make(map[int]int, len(inorder))
 	for i := 0; i < len(inorder); i++ {
-		hmap[inorder[i]] = i
+		inorderMap[inorder[i]] = i
 	}
 
-	root := dfsBuildTree(preorder, inorder, hmap, 0, 0, len(inorder)-1)
+	root := dfsBuildTree(preorder, inorderMap, 0, 0, len(inorder)-1)
 	return root
 }
diff --git a/codes/java/chapter_divide_and_conquer/build_tree.java b/codes/java/chapter_divide_and_conquer/build_tree.java
index 082ff5f6c..ca1085db7 100644
--- a/codes/java/chapter_divide_and_conquer/build_tree.java
+++ b/codes/java/chapter_divide_and_conquer/build_tree.java
@@ -11,18 +11,18 @@ import java.util.*;
 
 public class build_tree {
     /* 构建二叉树：分治 */
-    static TreeNode dfs(int[] preorder, int[] inorder, Map<Integer, Integer> hmap, int i, int l, int r) {
+    static TreeNode dfs(int[] preorder, Map<Integer, Integer> inorderMap, int i, int l, int r) {
         // 子树区间为空时终止
         if (r - l < 0)
             return null;
         // 初始化根节点
         TreeNode root = new TreeNode(preorder[i]);
         // 查询 m ，从而划分左右子树
-        int m = hmap.get(preorder[i]);
+        int m = inorderMap.get(preorder[i]);
         // 子问题：构建左子树
-        root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
+        root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
         // 子问题：构建右子树
-        root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
+        root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
         // 返回根节点
         return root;
     }
@@ -30,11 +30,11 @@ public class build_tree {
     /* 构建二叉树 */
     static TreeNode buildTree(int[] preorder, int[] inorder) {
         // 初始化哈希表，存储 inorder 元素到索引的映射
-        Map<Integer, Integer> hmap = new HashMap<>();
+        Map<Integer, Integer> inorderMap = new HashMap<>();
         for (int i = 0; i < inorder.length; i++) {
-            hmap.put(inorder[i], i);
+            inorderMap.put(inorder[i], i);
         }
-        TreeNode root = dfs(preorder, inorder, hmap, 0, 0, inorder.length - 1);
+        TreeNode root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
         return root;
     }
 
diff --git a/codes/javascript/chapter_divide_and_conquer/build_tree.js b/codes/javascript/chapter_divide_and_conquer/build_tree.js
index 67100bf58..1505b0495 100644
--- a/codes/javascript/chapter_divide_and_conquer/build_tree.js
+++ b/codes/javascript/chapter_divide_and_conquer/build_tree.js
@@ -8,17 +8,17 @@ const { printTree } = require('../modules/PrintUtil');
 const { TreeNode } = require('../modules/TreeNode');
 
 /* 构建二叉树：分治 */
-function dfs(preorder, inorder, hmap, i, l, r) {
+function dfs(preorder, inorderMap, i, l, r) {
     // 子树区间为空时终止
     if (r - l < 0) return null;
     // 初始化根节点
     const root = new TreeNode(preorder[i]);
     // 查询 m ，从而划分左右子树
-    const m = hmap.get(preorder[i]);
+    const m = inorderMap.get(preorder[i]);
     // 子问题：构建左子树
-    root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
+    root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
     // 子问题：构建右子树
-    root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
+    root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
     // 返回根节点
     return root;
 }
@@ -26,11 +26,11 @@ function dfs(preorder, inorder, hmap, i, l, r) {
 /* 构建二叉树 */
 function buildTree(preorder, inorder) {
     // 初始化哈希表，存储 inorder 元素到索引的映射
-    let hmap = new Map();
+    let inorderMap = new Map();
     for (let i = 0; i < inorder.length; i++) {
-        hmap.set(inorder[i], i);
+        inorderMap.set(inorder[i], i);
     }
-    const root = dfs(preorder, inorder, hmap, 0, 0, inorder.length - 1);
+    const root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
     return root;
 }
 
diff --git a/codes/python/chapter_divide_and_conquer/build_tree.py b/codes/python/chapter_divide_and_conquer/build_tree.py
index b8b2db293..970f1d4a4 100644
--- a/codes/python/chapter_divide_and_conquer/build_tree.py
+++ b/codes/python/chapter_divide_and_conquer/build_tree.py
@@ -12,8 +12,7 @@ from modules import *
 
 def dfs(
     preorder: list[int],
-    inorder: list[int],
-    hmap: dict[int, int],
+    inorder_map: dict[int, int],
     i: int,
     l: int,
     r: int,
@@ -25,11 +24,11 @@ def dfs(
     # 初始化根节点
     root = TreeNode(preorder[i])
     # 查询 m ，从而划分左右子树
-    m = hmap[preorder[i]]
+    m = inorder_map[preorder[i]]
     # 子问题：构建左子树
-    root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1)
+    root.left = dfs(preorder, inorder_map, i + 1, l, m - 1)
     # 子问题：构建右子树
-    root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r)
+    root.right = dfs(preorder, inorder_map, i + 1 + m - l, m + 1, r)
     # 返回根节点
     return root
 
@@ -37,8 +36,8 @@ def dfs(
 def build_tree(preorder: list[int], inorder: list[int]) -> TreeNode | None:
     """构建二叉树"""
     # 初始化哈希表，存储 inorder 元素到索引的映射
-    hmap = {val: i for i, val in enumerate(inorder)}
-    root = dfs(preorder, inorder, hmap, 0, 0, len(inorder) - 1)
+    inorder_map = {val: i for i, val in enumerate(inorder)}
+    root = dfs(preorder, inorder_map, 0, 0, len(inorder) - 1)
     return root
 
 
diff --git a/codes/rust/chapter_divide_and_conquer/build_tree.rs b/codes/rust/chapter_divide_and_conquer/build_tree.rs
index 3478e3ab6..76f987764 100644
--- a/codes/rust/chapter_divide_and_conquer/build_tree.rs
+++ b/codes/rust/chapter_divide_and_conquer/build_tree.rs
@@ -10,17 +10,17 @@ include!("../include/include.rs");
 use tree_node::TreeNode;
 
 /* 构建二叉树：分治 */
-fn dfs(preorder: &[i32], inorder: &[i32], hmap: &HashMap<i32, i32>, i: i32, l: i32, r: i32) -> Option<Rc<RefCell<TreeNode>>> {
+fn dfs(preorder: &[i32], inorderMap: &HashMap<i32, i32>, i: i32, l: i32, r: i32) -> Option<Rc<RefCell<TreeNode>>> {
     // 子树区间为空时终止
     if r - l < 0 { return None; }
     // 初始化根节点
     let root = TreeNode::new(preorder[i as usize]);
     // 查询 m ，从而划分左右子树
-    let m = hmap.get(&preorder[i as usize]).unwrap();
+    let m = inorderMap.get(&preorder[i as usize]).unwrap();
     // 子问题：构建左子树
-    root.borrow_mut().left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
+    root.borrow_mut().left = dfs(preorder, inorderMap, i + 1, l, m - 1);
     // 子问题：构建右子树
-    root.borrow_mut().right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
+    root.borrow_mut().right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
     // 返回根节点
     Some(root)
 }
@@ -28,11 +28,11 @@ fn dfs(preorder: &[i32], inorder: &[i32], hmap: &HashMap<i32, i32>, i: i32, l: i
 /* 构建二叉树 */
 fn build_tree(preorder: &[i32], inorder: &[i32]) -> Option<Rc<RefCell<TreeNode>>> {
     // 初始化哈希表，存储 inorder 元素到索引的映射
-    let mut hmap: HashMap<i32, i32> = HashMap::new();
+    let mut inorderMap: HashMap<i32, i32> = HashMap::new();
     for i in 0..inorder.len() {
-        hmap.insert(inorder[i], i as i32);
+        inorderMap.insert(inorder[i], i as i32);
     }
-    let root = dfs(preorder, inorder, &hmap, 0, 0, inorder.len() as i32 - 1);
+    let root = dfs(preorder, &inorderMap, 0, 0, inorder.len() as i32 - 1);
     root
 }
 
diff --git a/codes/swift/chapter_divide_and_conquer/build_tree.swift b/codes/swift/chapter_divide_and_conquer/build_tree.swift
index 048ffab1a..bd94ba467 100644
--- a/codes/swift/chapter_divide_and_conquer/build_tree.swift
+++ b/codes/swift/chapter_divide_and_conquer/build_tree.swift
@@ -7,7 +7,7 @@
 import utils
 
 /* 构建二叉树：分治 */
-func dfs(preorder: [Int], inorder: [Int], hmap: [Int: Int], i: Int, l: Int, r: Int) -> TreeNode? {
+func dfs(preorder: [Int], inorderMap: [Int: Int], i: Int, l: Int, r: Int) -> TreeNode? {
     // 子树区间为空时终止
     if r - l < 0 {
         return nil
@@ -15,11 +15,11 @@ func dfs(preorder: [Int], inorder: [Int], hmap: [Int: Int], i: Int, l: Int, r: I
     // 初始化根节点
     let root = TreeNode(x: preorder[i])
     // 查询 m ，从而划分左右子树
-    let m = hmap[preorder[i]]!
+    let m = inorderMap[preorder[i]]!
     // 子问题：构建左子树
-    root.left = dfs(preorder: preorder, inorder: inorder, hmap: hmap, i: i + 1, l: l, r: m - 1)
+    root.left = dfs(preorder: preorder, inorderMap: inorderMap, i: i + 1, l: l, r: m - 1)
     // 子问题：构建右子树
-    root.right = dfs(preorder: preorder, inorder: inorder, hmap: hmap, i: i + 1 + m - l, l: m + 1, r: r)
+    root.right = dfs(preorder: preorder, inorderMap: inorderMap, i: i + 1 + m - l, l: m + 1, r: r)
     // 返回根节点
     return root
 }
@@ -27,8 +27,8 @@ func dfs(preorder: [Int], inorder: [Int], hmap: [Int: Int], i: Int, l: Int, r: I
 /* 构建二叉树 */
 func buildTree(preorder: [Int], inorder: [Int]) -> TreeNode? {
     // 初始化哈希表，存储 inorder 元素到索引的映射
-    let hmap = inorder.enumerated().reduce(into: [:]) { $0[$1.element] = $1.offset }
-    return dfs(preorder: preorder, inorder: inorder, hmap: hmap, i: 0, l: 0, r: inorder.count - 1)
+    let inorderMap = inorder.enumerated().reduce(into: [:]) { $0[$1.element] = $1.offset }
+    return dfs(preorder: preorder, inorderMap: inorderMap, i: 0, l: 0, r: inorder.count - 1)
 }
 
 @main
diff --git a/codes/typescript/chapter_divide_and_conquer/build_tree.ts b/codes/typescript/chapter_divide_and_conquer/build_tree.ts
index 69f4afa04..d47b95450 100644
--- a/codes/typescript/chapter_divide_and_conquer/build_tree.ts
+++ b/codes/typescript/chapter_divide_and_conquer/build_tree.ts
@@ -10,8 +10,7 @@ import { TreeNode } from '../modules/TreeNode';
 /* 构建二叉树：分治 */
 function dfs(
     preorder: number[],
-    inorder: number[],
-    hmap: Map<number, number>,
+    inorderMap: Map<number, number>,
     i: number,
     l: number,
     r: number
@@ -21,11 +20,11 @@ function dfs(
     // 初始化根节点
     const root: TreeNode = new TreeNode(preorder[i]);
     // 查询 m ，从而划分左右子树
-    const m = hmap.get(preorder[i]);
+    const m = inorderMap.get(preorder[i]);
     // 子问题：构建左子树
-    root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
+    root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
     // 子问题：构建右子树
-    root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
+    root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
     // 返回根节点
     return root;
 }
@@ -33,11 +32,11 @@ function dfs(
 /* 构建二叉树 */
 function buildTree(preorder: number[], inorder: number[]): TreeNode | null {
     // 初始化哈希表，存储 inorder 元素到索引的映射
-    let hmap = new Map<number, number>();
+    let inorderMap = new Map<number, number>();
     for (let i = 0; i < inorder.length; i++) {
-        hmap.set(inorder[i], i);
+        inorderMap.set(inorder[i], i);
     }
-    const root = dfs(preorder, inorder, hmap, 0, 0, inorder.length - 1);
+    const root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
     return root;
 }
 
diff --git a/docs/chapter_dynamic_programming/edit_distance_problem.assets/edit_distance_dp_step8.png b/docs/chapter_dynamic_programming/edit_distance_problem.assets/edit_distance_dp_step8.png
index 4d7b43a05..c9620a9d4 100644
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diff --git a/docs/chapter_searching/replace_linear_by_hashing.assets/two_sum_hashtable_step2.png b/docs/chapter_searching/replace_linear_by_hashing.assets/two_sum_hashtable_step2.png
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