From 2f8829d3f699e277a1077827911077d7d4137771 Mon Sep 17 00:00:00 2001
From: krahets <krahets@163.com>
Date: Tue, 15 Nov 2022 04:55:19 +0800
Subject: [PATCH] Add section of binary search tree. Make all table align
 center.

---
 .../java/chapter_tree/binary_search_tree.java | 146 ++++++++++++++++++
 docs/index.md                                 |   2 +
 docs/stylesheets/extra.css                    |  12 +-
 mkdocs.yml                                    |   2 +-
 4 files changed, 160 insertions(+), 2 deletions(-)
 create mode 100644 codes/java/chapter_tree/binary_search_tree.java

diff --git a/codes/java/chapter_tree/binary_search_tree.java b/codes/java/chapter_tree/binary_search_tree.java
new file mode 100644
index 0000000..d338937
--- /dev/null
+++ b/codes/java/chapter_tree/binary_search_tree.java
@@ -0,0 +1,146 @@
+package chapter_tree;
+
+import java.util.*;
+import include.*;
+
+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
+    }
+
+    /* 获取二叉树根结点 */
+    public TreeNode getRoot() {
+        return root;
+    }
+
+    /* 构建二叉搜索树 */
+    public TreeNode buildTree(int[] nums, int i, int j) {
+        if (i > j) return null;
+        // 将数组中间结点作为根结点
+        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;
+    }
+
+    /* 查找结点 */
+    public TreeNode search(int num) {
+        TreeNode cur = root;
+        // 循环查找，越过叶结点后跳出
+        while (cur != null) {
+            // 目标结点在 root 的右子树中
+            if (cur.val < num) cur = cur.right;
+            // 目标结点在 root 的左子树中
+            else if (cur.val > num) cur = cur.left;
+            // 找到目标结点，跳出循环
+            else break;
+        }
+        // 返回目标结点
+        return cur;
+    }
+
+    /* 插入结点 */
+    public TreeNode insert(int num) {
+        // 若树为空，直接提前返回
+        if (root == null) return null;
+        TreeNode cur = root, pre = null;
+        // 循环查找，越过叶结点后跳出
+        while (cur != null) {
+            // 找到重复结点，直接返回
+            if (cur.val == num) return null;
+            pre = cur;
+            // 插入位置在 root 的右子树中
+            if (cur.val < num) cur = cur.right;
+            // 插入位置在 root 的左子树中
+            else cur = cur.left;
+        }
+        // 插入结点 val
+        TreeNode node = new TreeNode(num);
+        if (pre.val < num) pre.right = node;
+        else pre.left = node;
+        return node;
+    }
+
+    /* 删除结点 */
+    public TreeNode remove(int num) {
+        // 若树为空，直接提前返回
+        if (root == null) return null;
+        TreeNode cur = root, pre = null;
+        // 循环查找，越过叶结点后跳出
+        while (cur != null) {
+            // 找到待删除结点，跳出循环
+            if (cur.val == num) break;
+            pre = cur;
+            // 待删除结点在 root 的右子树中
+            if (cur.val < num) cur = cur.right;
+            // 待删除结点在 root 的左子树中
+            else cur = cur.left;
+        }
+        // 若无待删除结点，则直接返回
+        if (cur == null) return null;
+        // 子结点数量 = 0 or 1
+        if (cur.left == null || cur.right == null) {
+            // 当子结点数量 = 0 / 1 时， child = null / 该子结点
+            TreeNode child = cur.left != null ? cur.left : cur.right;
+            // 删除结点 cur
+            if (pre.left == cur) pre.left = child;
+            else pre.right = child;
+        }
+        // 子结点数量 = 2
+        else {
+            // 获取中序遍历中 cur 的下一个结点
+            TreeNode nex = min(cur.right);
+            int tmp = nex.val;
+            // 递归删除结点 nex
+            remove(nex.val);
+            // 将 nex 的值复制给 cur
+            cur.val = tmp;
+        }
+        return cur;
+    }
+
+    /* 获取最小结点 */
+    public TreeNode min(TreeNode root) {
+        if (root == null) return root;
+        // 循环访问左子结点，直到叶结点时为最小结点，跳出
+        while (root.left != null) {
+            root = root.left;
+        }
+        return root;
+    }
+}
+
+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);
+        System.out.println("\n初始化的二叉树为\n");
+        PrintUtil.printTree(bst.getRoot());
+
+        /* 查找结点 */
+        TreeNode node = bst.search(5);
+        System.out.println("\n查找到的结点对象为 " + node + "，结点值 = " + node.val);
+
+        /* 插入结点 */
+        node = bst.insert(16);
+        System.out.println("\n插入结点 16 后，二叉树为\n");
+        PrintUtil.printTree(bst.getRoot());
+
+        /* 删除结点 */
+        bst.remove(1);
+        System.out.println("\n删除结点 1 后，二叉树为\n");
+        PrintUtil.printTree(bst.getRoot());
+        bst.remove(2);
+        System.out.println("\n删除结点 2 后，二叉树为\n");
+        PrintUtil.printTree(bst.getRoot());
+        bst.remove(4);
+        System.out.println("\n删除结点 4 后，二叉树为\n");
+        PrintUtil.printTree(bst.getRoot());
+    }
+}
diff --git a/docs/index.md b/docs/index.md
index 9edc7fa..2b0b34a 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -23,3 +23,5 @@ TODO
 | 更新：列表 Java 代码、配图 | 2022-11-07 |
 | 新增：栈与队列 | 2022-11-09 |
 | 新增：树     | 2022-11-12 |
+| 新增：二叉搜索树，<br />更新：二叉树、表格居中 | 2022-11-13 |
+| 更新：二叉搜索树 | 2022-11-14 |
diff --git a/docs/stylesheets/extra.css b/docs/stylesheets/extra.css
index 19a1b72..9ba484d 100644
--- a/docs/stylesheets/extra.css
+++ b/docs/stylesheets/extra.css
@@ -19,4 +19,14 @@
 
     --md-typeset-color: #FEFEFE;
     --md-typeset-a-color: #31BC5A;
-}
\ No newline at end of file
+}
+
+/* Center Markdown Tables (requires md_in_html extension) */
+.center-table {
+    text-align: center;
+}
+
+.md-typeset .center-table :is(td,th):not([align]) {
+    /* Reset alignment for table cells */
+    text-align: initial;
+}
diff --git a/mkdocs.yml b/mkdocs.yml
index 468f7a2..63c2ea0 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -17,7 +17,7 @@ theme:
   features:
     - announce.dismiss
     - content.code.annotate
-    # - content.tabs.link
+    - content.tabs.link
     - content.tooltips
     # - header.autohide
     # - navigation.expand