add JavaScript codes for Tree

codes/javascript/chapter_tree/binary_search_tree.js

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+/**
+ * File: binary_tree.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const Tree = require("../include/TreeNode");
+const { printTree } = require("../include/PrintUtil");
+
+/* 二叉搜索树 */
+var 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
+}
+
+/* 获取二叉树根结点 */
+function getRoot() {
+    return root;
+}
+
+/* 构建二叉搜索树 */
+function buildTree(nums, i, j) {
+    if (i > j) return null;
+    // 将数组中间结点作为根结点
+    let mid = Math.floor((i + j) / 2);
+    let root = new Tree.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 */
+function search(num) {
+    let 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 */
+function insert(num) {
+    // 若树为空，直接提前返回
+    if (root === null) return null;
+    let 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
+    let node = new Tree.TreeNode(num);
+    if (pre.val < num) pre.right = node;
+    else pre.left = node;
+    return node;
+}
+
+/* 删除结点 */
+function remove(num) {
+    // 若树为空，直接提前返回
+    if (root === null) return null;
+    let 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
+        let 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
+        let nex = min(cur.right);
+        let 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 */
+function min(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;
+}
+
+/* Driver Code */
+/* 初始化二叉搜索树 */
+var nums = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 ];
+BinarySearchTree(nums)
+console.log("\n初始化的二叉树为\n");
+printTree(getRoot());
+
+/* 查找结点 */
+let node = search(5);
+console.log("\n查找到的结点对象为 " + node + "，结点值 = " + node.val);
+
+/* 插入结点 */
+node = insert(16);
+console.log("\n插入结点 16 后，二叉树为\n");
+printTree(getRoot());
+
+/* 删除结点 */
+remove(1);
+console.log("\n删除结点 1 后，二叉树为\n");
+printTree(getRoot());
+remove(2);
+console.log("\n删除结点 2 后，二叉树为\n");
+printTree(getRoot());
+remove(4);
+console.log("\n删除结点 4 后，二叉树为\n");
+printTree(getRoot());

codes/javascript/chapter_tree/binary_tree.js

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+/**
+ * File: binary_tree.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const Tree = require("../include/TreeNode");
+const { printTree } = require("../include/PrintUtil");
+
+/* 初始化二叉树 */
+// 初始化结点
+let n1 = new Tree.TreeNode(1),
+n2 = new Tree.TreeNode(2),
+n3 = new Tree.TreeNode(3),
+n4 = new Tree.TreeNode(4),
+n5 = new Tree.TreeNode(5);
+// 构建引用指向（即指针）
+n1.left = n2;
+n1.right = n3;
+n2.left = n4;
+n2.right = n5;
+console.log("\n初始化二叉树\n")
+printTree(n1)
+
+/* 插入与删除结点 */
+let P = new Tree.TreeNode(0);
+// 在 n1 -> n2 中间插入结点 P
+n1.left = P;
+P.left = n2;
+console.log("\n插入结点 P 后\n");
+printTree(n1);
+// 删除结点 P
+n1.left = n2;
+console.log("\n删除结点 P 后\n");
+printTree(n1);

codes/javascript/chapter_tree/binary_tree_bfs.js

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+/**
+ * File: binary_tree.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const { arrToTree } = require("../include/TreeNode");
+const { printTree } = require("../include/PrintUtil");
+
+/* 层序遍历 */
+function hierOrder(root) {
+    // 初始化队列，加入根结点
+    let queue = [root];
+    // 初始化一个列表，用于保存遍历序列
+    let list = [];
+    while (queue.length) {
+        let node = queue.shift();  // 队列出队
+        list.push(node.val);          // 保存结点
+        if (node.left)
+            queue.push(node.left);    // 左子结点入队
+        if (node.right)
+            queue.push(node.right);   // 右子结点入队
+
+    }
+    return list;
+}
+
+/* Driver Code */
+/* 初始化二叉树 */
+// 这里借助了一个从数组直接生成二叉树的函数
+var root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null ]);
+console.log("\n初始化二叉树\n");
+printTree(root);
+
+/* 层序遍历 */
+let list = hierOrder(root);
+console.log("\n层序遍历的结点打印序列 = " + list);

codes/javascript/chapter_tree/binary_tree_dfs.js

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+/**
+ * File: binary_tree.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const { arrToTree } = require("../include/TreeNode");
+const { printTree } = require("../include/PrintUtil");
+
+// 初始化列表，用于存储遍历序列
+var list = []
+
+/* 前序遍历 */
+function preOrder(root){
+    if (root === null) return;
+    // 访问优先级：根结点 -> 左子树 -> 右子树
+    list.push(root.val);
+    preOrder(root.left);
+    preOrder(root.right);
+ }
+
+/* 中序遍历 */
+function inOrder(root) {
+    if (root === null) return;
+    // 访问优先级：左子树 -> 根结点 -> 右子树
+    inOrder(root.left);
+    list.push(root.val);
+    inOrder(root.right);
+}
+
+/* 后序遍历 */
+function postOrder(root) {
+    if (root === null) return;
+    // 访问优先级：左子树 -> 右子树 -> 根结点
+    postOrder(root.left);
+    postOrder(root.right);
+    list.push(root.val);
+}
+
+/* Driver Code */
+/* 初始化二叉树 */
+// 这里借助了一个从数组直接生成二叉树的函数
+var root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null]);
+console.log("\n初始化二叉树\n");
+printTree(root);
+
+/* 前序遍历 */
+list.length = 0;
+preOrder(root);
+console.log("\n前序遍历的结点打印序列 = " + list);
+
+/* 中序遍历 */
+list.length = 0;
+inOrder(root);
+console.log("\n中序遍历的结点打印序列 = " + list);
+
+/* 后序遍历 */
+list.length = 0;
+postOrder(root);
+console.log("\n后序遍历的结点打印序列 = " + list);
+

codes/javascript/include/PrintUtil.js

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+/**
+ * File: PrintUtil.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+function Trunk(prev, str) {
+    this.prev = prev;
+    this.str = str;
+}
+
+/**
+ * Print a linked list
+ * @param head
+ */
+function printLinkedList(head) {
+    let list = [];
+    while (head !== null) {
+        list.push(head.val.toString());
+        head = head.next;
+    }
+    console.log(list.join(" -> "));
+}
+
+/**
+ * The interface of the tree printer
+ * This tree printer is borrowed from TECHIE DELIGHT
+ * https://www.techiedelight.com/c-program-print-binary-tree/
+ * @param root
+ */
+function printTree(root) {
+    printTree(root, null, false);
+}
+
+/**
+ * Print a binary tree
+ * @param root
+ * @param prev
+ * @param isLeft
+ */
+function printTree(root, prev, isLeft) {
+    if (root === null) {
+        return;
+    }
+
+    let prev_str = "    ";
+    let trunk = new Trunk(prev, prev_str);
+
+    printTree(root.right, trunk, true);
+
+    if (!prev) {
+        trunk.str = "———";
+    } else if (isLeft) {
+        trunk.str = "/———";
+        prev_str = "   |";
+    } else {
+        trunk.str = "\\———";
+        prev.str = prev_str;
+    }
+
+    showTrunks(trunk);
+    console.log(" " + root.val);
+
+    if (prev) {
+        prev.str = prev_str;
+    }
+    trunk.str = "   |";
+
+    printTree(root.left, trunk, false);
+}
+
+/**
+ * Helper function to print branches of the binary tree
+ * @param p
+ */
+function showTrunks(p) {
+    if (!p) {
+        return;
+    }
+
+    showTrunks(p.prev);
+    console.log(p.str);
+}
+
+module.exports = { 
+    printTree,
+    printLinkedList,
+}