fix binary_search_tree code

codes/c/chapter_tree/binary_search_tree.c

@@ -70,9 +70,11 @@ TreeNode *search(binarySearchTree *bst, int num) {
 
 /* 插入节点 */
 void insert(binarySearchTree *bst, int num) {
-    // 若树为空，直接提前返回
-    if (bst->root == NULL)
+    // 若树为空，则初始化根节点
+    if (bst->root == NULL) {
+        bst->root = newTreeNode(num);
         return;
+    }
     TreeNode *cur = bst->root, *pre = NULL;
     // 循环查找，越过叶节点后跳出
     while (cur != NULL) {

codes/cpp/chapter_tree/binary_search_tree.cpp

@@ -12,11 +12,13 @@ class BinarySearchTree {
     TreeNode *root;
 
   public:
-    BinarySearchTree(vector<int> nums) {
-        sort(nums.begin(), nums.end());             // 排序数组
-        root = buildTree(nums, 0, nums.size() - 1); // 构建二叉搜索树
+    /* 构造方法 */
+    BinarySearchTree() {
+        // 初始化空树
+        root = nullptr;
     }
 
+    /* 析构方法 */
     ~BinarySearchTree() {
         freeMemoryTree(root);
     }
@@ -26,19 +28,6 @@ class BinarySearchTree {
         return root;
     }
 
-    /* 构建二叉搜索树 */
-    TreeNode *buildTree(vector<int> nums, int i, int j) {
-        if (i > j)
-            return nullptr;
-        // 将数组中间节点作为根节点
-        int mid = (i + j) / 2;
-        TreeNode *root = new TreeNode(nums[mid]);
-        // 递归建立左子树和右子树
-        root->left = buildTree(nums, i, mid - 1);
-        root->right = buildTree(nums, mid + 1, j);
-        return root;
-    }
-
     /* 查找节点 */
     TreeNode *search(int num) {
         TreeNode *cur = root;
@@ -60,9 +49,11 @@ class BinarySearchTree {
 
     /* 插入节点 */
     void insert(int num) {
-        // 若树为空，直接提前返回
-        if (root == nullptr)
+        // 若树为空，则初始化根节点
+        if (root == nullptr) {
+            root = new TreeNode(num);
             return;
+        }
         TreeNode *cur = root, *pre = nullptr;
         // 循环查找，越过叶节点后跳出
         while (cur != nullptr) {
@@ -143,8 +134,12 @@ class BinarySearchTree {
 /* Driver Code */
 int main() {
     /* 初始化二叉搜索树 */
-    vector<int> nums = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15};
-    BinarySearchTree *bst = new BinarySearchTree(nums);
+    BinarySearchTree *bst = new BinarySearchTree();
+    // 请注意，不同的插入顺序会生成不同的二叉树，该序列可以生成一个完美二叉树
+    vector<int> nums = {8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15};
+    for (int num : nums) {
+        bst->insert(num);
+    }
     cout << endl << "初始化的二叉树为\n" << endl;
     printTree(bst->getRoot());
 

codes/csharp/chapter_tree/binary_search_tree.cs

@@ -54,9 +54,11 @@ class BinarySearchTree {
 
     /* 插入节点 */
     public void insert(int num) {
-        // 若树为空，直接提前返回
-        if (root == null)
+        // 若树为空，则初始化根节点
+        if (root == null) {
+            root = new TreeNode(num);
             return;
+        }
         TreeNode? cur = root, pre = null;
         // 循环查找，越过叶节点后跳出
         while (cur != null) {

codes/dart/chapter_tree/binary_search_tree.dart

@@ -56,8 +56,11 @@ class BinarySearchTree {
 
   /* 插入节点 */
   void insert(int num) {
-    // 若树为空，直接提前返回
-    if (_root == null) return;
+    // 若树为空，则初始化根节点
+    if (_root == null) {
+      _root = TreeNode(num);
+      return;
+    }
     TreeNode? cur = _root;
     TreeNode? pre = null;
     // 循环查找，越过叶节点后跳出

codes/go/chapter_tree/binary_search_tree.go

@@ -5,8 +5,6 @@
 package chapter_tree
 
 import (
-	"sort"
-
 	. "github.com/krahets/hello-algo/pkg"
 )
 
@@ -14,29 +12,13 @@ type binarySearchTree struct {
 	root *TreeNode
 }
 
-func newBinarySearchTree(nums []int) *binarySearchTree {
-	// 排序数组
-	sort.Ints(nums)
-	// 构建二叉搜索树
+func newBinarySearchTree() *binarySearchTree {
 	bst := &binarySearchTree{}
-	bst.root = bst.buildTree(nums, 0, len(nums)-1)
+	// 初始化空树
+	bst.root = nil
 	return bst
 }
 
-/* 构建二叉搜索树 */
-func (bst *binarySearchTree) buildTree(nums []int, left, right int) *TreeNode {
-	if left > right {
-		return nil
-	}
-	// 将数组中间节点作为根节点
-	middle := left + (right-left)>>1
-	root := NewTreeNode(nums[middle])
-	// 递归构建左子树和右子树
-	root.Left = bst.buildTree(nums, left, middle-1)
-	root.Right = bst.buildTree(nums, middle+1, right)
-	return root
-}
-
 /* 获取根节点 */
 func (bst *binarySearchTree) getRoot() *TreeNode {
 	return bst.root
@@ -65,8 +47,9 @@ func (bst *binarySearchTree) search(num int) *TreeNode {
 /* 插入节点 */
 func (bst *binarySearchTree) insert(num int) {
 	cur := bst.root
-	// 若树为空，直接提前返回
+	// 若树为空，则初始化根节点
 	if cur == nil {
+		bst.root = NewTreeNode(num)
 		return
 	}
 	// 待插入节点之前的节点位置

codes/go/chapter_tree/binary_search_tree_test.go

@@ -10,8 +10,12 @@ import (
 )
 
 func TestBinarySearchTree(t *testing.T) {
-	nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
-	bst := newBinarySearchTree(nums)
+	bst := newBinarySearchTree()
+	nums := []int{8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15}
+	// 请注意，不同的插入顺序会生成不同的二叉树，该序列可以生成一个完美二叉树
+	for _, num := range nums {
+		bst.insert(num)
+	}
 	fmt.Println("\n初始化的二叉树为:")
 	bst.print()
 

codes/java/chapter_tree/binary_search_tree.java

@@ -6,16 +6,16 @@
 
 package chapter_tree;
 
-import java.util.*;
 import utils.*;
 
 /* 二叉搜索树 */
 class BinarySearchTree {
     private TreeNode root;
 
-    public BinarySearchTree(int[] nums) {
-        Arrays.sort(nums); // 排序数组
-        root = buildTree(nums, 0, nums.length - 1); // 构建二叉搜索树
+    /* 构造方法 */
+    public BinarySearchTree() {
+        // 初始化空树
+        root = null;
     }
 
     /* 获取二叉树根节点 */
@@ -23,19 +23,6 @@ class BinarySearchTree {
         return root;
     }
 
-    /* 构建二叉搜索树 */
-    public TreeNode buildTree(int[] nums, int i, int j) {
-        if (i > j)
-            return null;
-        // 将数组中间节点作为根节点
-        int mid = (i + j) / 2;
-        TreeNode root = new TreeNode(nums[mid]);
-        // 递归建立左子树和右子树
-        root.left = buildTree(nums, i, mid - 1);
-        root.right = buildTree(nums, mid + 1, j);
-        return root;
-    }
-
     /* 查找节点 */
     public TreeNode search(int num) {
         TreeNode cur = root;
@@ -57,9 +44,11 @@ class BinarySearchTree {
 
     /* 插入节点 */
     public void insert(int num) {
-        // 若树为空，直接提前返回
-        if (root == null)
+        // 若树为空，则初始化根节点
+        if (root == null) {
+            root = new TreeNode(num);
             return;
+        }
         TreeNode cur = root, pre = null;
         // 循环查找，越过叶节点后跳出
         while (cur != null) {
@@ -137,8 +126,12 @@ class BinarySearchTree {
 public class binary_search_tree {
     public static void main(String[] args) {
         /* 初始化二叉搜索树 */
-        int[] nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
-        BinarySearchTree bst = new BinarySearchTree(nums);
+        BinarySearchTree bst = new BinarySearchTree();
+        // 请注意，不同的插入顺序会生成不同的二叉树，该序列可以生成一个完美二叉树
+        int[] nums = { 8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15 };
+        for (int num : nums) {
+            bst.insert(num);
+        }
         System.out.println("\n初始化的二叉树为\n");
         PrintUtil.printTree(bst.getRoot());
 

codes/javascript/chapter_tree/avl_tree.js

@@ -9,7 +9,7 @@ const { printTree } = require('../modules/PrintUtil');
 
 /* AVL 树*/
 class AVLTree {
-    /*构造方法*/
+    /* 构造方法 */
     constructor() {
         this.root = null; //根节点
     }

codes/javascript/chapter_tree/binary_search_tree.js

@@ -8,138 +8,132 @@ const { TreeNode } = require('../modules/TreeNode');
 const { printTree } = require('../modules/PrintUtil');
 
 /* 二叉搜索树 */
-let root;
-
-function BinarySearchTree(nums) {
-    nums.sort((a, b) => {
-        return a - b;
-    }); // 排序数组
-    root = buildTree(nums, 0, nums.length - 1); // 构建二叉搜索树
-}
-
-/* 获取二叉树根节点 */
-function getRoot() {
-    return root;
-}
-
-/* 构建二叉搜索树 */
-function buildTree(nums, i, j) {
-    if (i > j) return null;
-    // 将数组中间节点作为根节点
-    let mid = Math.floor((i + j) / 2);
-    let root = new TreeNode(nums[mid]);
-    // 递归建立左子树和右子树
-    root.left = buildTree(nums, i, mid - 1);
-    root.right = buildTree(nums, mid + 1, j);
-    return root;
-}
-
-/* 查找节点 */
-function search(num) {
-    let cur = root;
-    // 循环查找，越过叶节点后跳出
-    while (cur !== null) {
-        // 目标节点在 cur 的右子树中
-        if (cur.val < num) cur = cur.right;
-        // 目标节点在 cur 的左子树中
-        else if (cur.val > num) cur = cur.left;
-        // 找到目标节点，跳出循环
-        else break;
+class BinarySearchTree {
+    /* 构造方法 */
+    constructor() {
+        // 初始化空树
+        this.root = null;
     }
-    // 返回目标节点
-    return cur;
-}
 
-/* 插入节点 */
-function insert(num) {
-    // 若树为空，直接提前返回
-    if (root === null) return;
-    let cur = root,
-        pre = null;
-    // 循环查找，越过叶节点后跳出
-    while (cur !== null) {
-        // 找到重复节点，直接返回
-        if (cur.val === num) return;
-        pre = cur;
-        // 插入位置在 cur 的右子树中
-        if (cur.val < num) cur = cur.right;
-        // 插入位置在 cur 的左子树中
-        else cur = cur.left;
+    /* 获取二叉树根节点 */
+    getRoot() {
+        return this.root;
     }
-    // 插入节点
-    let node = new TreeNode(num);
-    if (pre.val < num) pre.right = node;
-    else pre.left = node;
-}
 
-/* 删除节点 */
-function remove(num) {
-    // 若树为空，直接提前返回
-    if (root === null) return;
-    let cur = root,
-        pre = null;
-    // 循环查找，越过叶节点后跳出
-    while (cur !== null) {
-        // 找到待删除节点，跳出循环
-        if (cur.val === num) break;
-        pre = cur;
-        // 待删除节点在 cur 的右子树中
-        if (cur.val < num) cur = cur.right;
-        // 待删除节点在 cur 的左子树中
-        else cur = cur.left;
-    }
-    // 若无待删除节点，则直接返回
-    if (cur === null) return;
-    // 子节点数量 = 0 or 1
-    if (cur.left === null || cur.right === null) {
-        // 当子节点数量 = 0 / 1 时， child = null / 该子节点
-        let child = cur.left !== null ? cur.left : cur.right;
-        // 删除节点 cur
-        if (cur != root) {
-            if (pre.left === cur) pre.left = child;
-            else pre.right = child;
-        } else {
-            // 若删除节点为根节点，则重新指定根节点
-            root = child;
+    /* 查找节点 */
+    search(num) {
+        let cur = this.root;
+        // 循环查找，越过叶节点后跳出
+        while (cur !== null) {
+            // 目标节点在 cur 的右子树中
+            if (cur.val < num) cur = cur.right;
+            // 目标节点在 cur 的左子树中
+            else if (cur.val > num) cur = cur.left;
+            // 找到目标节点，跳出循环
+            else break;
         }
+        // 返回目标节点
+        return cur;
     }
-    // 子节点数量 = 2
-    else {
-        // 获取中序遍历中 cur 的下一个节点
-        let tmp = cur.right;
-        while (tmp.left !== null) {
-            tmp = tmp.left;
+
+    /* 插入节点 */
+    insert(num) {
+        // 若树为空，则初始化根节点
+        if (this.root === null) {
+            this.root = new TreeNode(num);
+            return;
+        }
+        let cur = this.root,
+            pre = null;
+        // 循环查找，越过叶节点后跳出
+        while (cur !== null) {
+            // 找到重复节点，直接返回
+            if (cur.val === num) return;
+            pre = cur;
+            // 插入位置在 cur 的右子树中
+            if (cur.val < num) cur = cur.right;
+            // 插入位置在 cur 的左子树中
+            else cur = cur.left;
+        }
+        // 插入节点
+        let node = new TreeNode(num);
+        if (pre.val < num) pre.right = node;
+        else pre.left = node;
+    }
+
+    /* 删除节点 */
+    remove(num) {
+        // 若树为空，直接提前返回
+        if (this.root === null) return;
+        let cur = this.root,
+            pre = null;
+        // 循环查找，越过叶节点后跳出
+        while (cur !== null) {
+            // 找到待删除节点，跳出循环
+            if (cur.val === num) break;
+            pre = cur;
+            // 待删除节点在 cur 的右子树中
+            if (cur.val < num) cur = cur.right;
+            // 待删除节点在 cur 的左子树中
+            else cur = cur.left;
+        }
+        // 若无待删除节点，则直接返回
+        if (cur === null) return;
+        // 子节点数量 = 0 or 1
+        if (cur.left === null || cur.right === null) {
+            // 当子节点数量 = 0 / 1 时， child = null / 该子节点
+            let child = cur.left !== null ? cur.left : cur.right;
+            // 删除节点 cur
+            if (cur !== this.root) {
+                if (pre.left === cur) pre.left = child;
+                else pre.right = child;
+            } else {
+                // 若删除节点为根节点，则重新指定根节点
+                this.root = child;
+            }
+        }
+        // 子节点数量 = 2
+        else {
+            // 获取中序遍历中 cur 的下一个节点
+            let tmp = cur.right;
+            while (tmp.left !== null) {
+                tmp = tmp.left;
+            }
+            // 递归删除节点 tmp
+            this.remove(tmp.val);
+            // 用 tmp 覆盖 cur
+            cur.val = tmp.val;
         }
-        // 递归删除节点 tmp
-        remove(tmp.val);
-        // 用 tmp 覆盖 cur
-        cur.val = tmp.val;
     }
 }
 
 /* Driver Code */
 /* 初始化二叉搜索树 */
-const nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
-BinarySearchTree(nums);
+const bst = new BinarySearchTree();
+// 请注意，不同的插入顺序会生成不同的二叉树，该序列可以生成一个完美二叉树
+const nums = [8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15];
+for (const num of nums) {
+    bst.insert(num);
+}
 console.log('\n初始化的二叉树为\n');
-printTree(getRoot());
+printTree(bst.getRoot());
 
 /* 查找节点 */
-let node = search(7);
+let node = bst.search(7);
 console.log('\n查找到的节点对象为 ' + node + '，节点值 = ' + node.val);
 
 /* 插入节点 */
-insert(16);
+bst.insert(16);
 console.log('\n插入节点 16 后，二叉树为\n');
-printTree(getRoot());
+printTree(bst.getRoot());
 
 /* 删除节点 */
-remove(1);
+bst.remove(1);
 console.log('\n删除节点 1 后，二叉树为\n');
-printTree(getRoot());
-remove(2);
+printTree(bst.getRoot());
+bst.remove(2);
 console.log('\n删除节点 2 后，二叉树为\n');
-printTree(getRoot());
-remove(4);
+printTree(bst.getRoot());
+bst.remove(4);
 console.log('\n删除节点 4 后，二叉树为\n');
-printTree(getRoot());
+printTree(bst.getRoot());

codes/python/chapter_tree/binary_search_tree.py

@@ -13,33 +13,18 @@ from modules import *
 class BinarySearchTree:
     """二叉搜索树"""
 
-    def __init__(self, nums: list[int]):
+    def __init__(self):
         """构造方法"""
-        nums.sort()
-        self.root = self.build_tree(nums, 0, len(nums) - 1)
+        # 初始化空树
+        self.__root = None
 
-    def build_tree(
-        self, nums: list[int], start_index: int, end_index: int
-    ) -> TreeNode | None:
-        """构建二叉搜索树"""
-        if start_index > end_index:
-            return None
-
-        # 将数组中间节点作为根节点
-        mid = (start_index + end_index) // 2
-        root = TreeNode(nums[mid])
-        # 递归建立左子树和右子树
-        root.left = self.build_tree(
-            nums=nums, start_index=start_index, end_index=mid - 1
-        )
-        root.right = self.build_tree(
-            nums=nums, start_index=mid + 1, end_index=end_index
-        )
-        return root
+    def get_root(self) -> TreeNode | None:
+        """获取二叉树根节点"""
+        return self.__root
 
     def search(self, num: int) -> TreeNode | None:
         """查找节点"""
-        cur: TreeNode | None = self.root
+        cur = self.__root
         # 循环查找，越过叶节点后跳出
         while cur is not None:
             # 目标节点在 cur 的右子树中
@@ -55,12 +40,12 @@ class BinarySearchTree:
 
     def insert(self, num: int):
         """插入节点"""
-        # 若树为空，直接提前返回
-        if self.root is None:
+        # 若树为空，则初始化根节点
+        if self.__root is None:
+            self.__root = TreeNode(num)
             return
-
         # 循环查找，越过叶节点后跳出
-        cur, pre = self.root, None
+        cur, pre = self.__root, None
         while cur is not None:
             # 找到重复节点，直接返回
             if cur.val == num:
@@ -72,7 +57,6 @@ class BinarySearchTree:
             # 插入位置在 cur 的左子树中
             else:
                 cur = cur.left
-
         # 插入节点
         node = TreeNode(num)
         if pre.val < num:
@@ -83,11 +67,10 @@ class BinarySearchTree:
     def remove(self, num: int):
         """删除节点"""
         # 若树为空，直接提前返回
-        if self.root is None:
+        if self.__root is None:
             return
-
         # 循环查找，越过叶节点后跳出
-        cur, pre = self.root, None
+        cur, pre = self.__root, None
         while cur is not None:
             # 找到待删除节点，跳出循环
             if cur.val == num:
@@ -108,14 +91,14 @@ class BinarySearchTree:
             # 当子节点数量 = 0 / 1 时， child = null / 该子节点
             child = cur.left or cur.right
             # 删除节点 cur
-            if cur != self.root:
+            if cur != self.__root:
                 if pre.left == cur:
                     pre.left = child
                 else:
                     pre.right = child
             else:
                 # 若删除节点为根节点，则重新指定根节点
-                self.root = child
+                self.__root = child
         # 子节点数量 = 2
         else:
             # 获取中序遍历中 cur 的下一个节点
@@ -131,10 +114,13 @@ class BinarySearchTree:
 """Driver Code"""
 if __name__ == "__main__":
     # 初始化二叉搜索树
-    nums = list(range(1, 16))  # [1, 2, ..., 15]
-    bst = BinarySearchTree(nums=nums)
+    bst = BinarySearchTree()
+    nums = [8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15]
+    # 请注意，不同的插入顺序会生成不同的二叉树，该序列可以生成一个完美二叉树
+    for num in nums:
+        bst.insert(num)
     print("\n初始化的二叉树为\n")
-    print_tree(bst.root)
+    print_tree(bst.get_root())
 
     # 查找节点
     node = bst.search(7)
@@ -143,17 +129,17 @@ if __name__ == "__main__":
     # 插入节点
     bst.insert(16)
     print("\n插入节点 16 后，二叉树为\n")
-    print_tree(bst.root)
+    print_tree(bst.get_root())
 
     # 删除节点
     bst.remove(1)
     print("\n删除节点 1 后，二叉树为\n")
-    print_tree(bst.root)
+    print_tree(bst.get_root())
 
     bst.remove(2)
     print("\n删除节点 2 后，二叉树为\n")
-    print_tree(bst.root)
+    print_tree(bst.get_root())
 
     bst.remove(4)
     print("\n删除节点 4 后，二叉树为\n")
-    print_tree(bst.root)
+    print_tree(bst.get_root())

codes/rust/chapter_tree/binary_search_tree.rs

@@ -74,8 +74,9 @@ impl BinarySearchTree {
 
     /* 插入节点 */
     pub fn insert(&mut self, num: i32) {
-        // 若树为空，直接提前返回
+        // 若树为空，则初始化根节点
         if self.root.is_none() {
+            self.root = TreeNode::new(num);
             return;
         }
         let mut cur = self.root.clone();

codes/swift/chapter_tree/binary_search_tree.swift

@@ -58,8 +58,9 @@ class BinarySearchTree {
 
     /* 插入节点 */
     func insert(num: Int) {
-        // 若树为空，直接提前返回
+        // 若树为空，则初始化根节点
         if root == nil {
+            root = TreeNode(x: num)
             return
         }
         var cur = root

codes/typescript/chapter_tree/binary_search_tree.ts

@@ -53,8 +53,9 @@ function search(num: number): TreeNode | null {
 
 /* 插入节点 */
 function insert(num: number): void {
-    // 若树为空，直接提前返回
+    // 若树为空，则初始化根节点
     if (root === null) {
+        root = new TreeNode(num);
         return;
     }
     let cur = root,

codes/zig/chapter_tree/binary_search_tree.zig

@@ -70,8 +70,11 @@ pub fn BinarySearchTree(comptime T: type) type {
 
         // 插入节点
         fn insert(self: *Self, num: T) !void {
-            // 若树为空，直接提前返回
-            if (self.root == null) return;
+            // 若树为空，则初始化根节点
+            if (self.root == null) {
+                self.root = try self.mem_allocator.create(inc.TreeNode(T));
+                return;
+            }
             var cur = self.root;
             var pre: ?*inc.TreeNode(T) = null;
             // 循环查找，越过叶节点后跳出