Add JavaScript and TypeScript code of preorder traversal (Chapter of Backtracking) (#490)

* Add JavaScript and TypeScript code of preorder traversal (Chapter of Backtracking)

* Update preorder_traversal_iii_compact.ts

codes/javascript/chapter_backtracking/preorder_traversal_i_compact.js

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+/**
+ * File: preorder_traversal_i_compact.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* 前序遍历：例题一 */
+function preOrder(root, res) {
+  if (root === null) {
+    return;
+  }
+  if (root.val === 7) {
+    // 记录解
+    res.push(root);
+  }
+  preOrder(root.left, res);
+  preOrder(root.right, res);
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 前序遍历
+const res = [];
+preOrder(root, res);
+
+console.log("\n输出所有值为 7 的节点");
+console.log(res.map(node => node.val));

codes/javascript/chapter_backtracking/preorder_traversal_ii_compact.js

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+/**
+ * File: preorder_traversal_ii_compact.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* 前序遍历：例题二 */
+function preOrder(root, path, res) {
+  if (root === null) {
+    return;
+  }
+  // 尝试
+  path.push(root);
+  if (root.val === 7) {
+    // 记录解
+    res.push([...path]);
+  }
+  preOrder(root.left, path, res);
+  preOrder(root.right, path, res);
+  // 回退
+  path.pop();
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 前序遍历
+const path = [];
+const res = [];
+preOrder(root, path, res);
+
+console.log("\n输出所有根节点到节点 7 的路径");
+res.forEach(path => {
+  console.log(path.map(node => node.val));
+});

codes/javascript/chapter_backtracking/preorder_traversal_iii_compact.js

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+/**
+ * File: preorder_traversal_iii_compact.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* 前序遍历：例题三 */
+function preOrder(root, path, res) {
+  // 剪枝
+  if (root === null || root.val === 3) {
+    return;
+  }
+  // 尝试
+  path.push(root);
+  if (root.val === 7) {
+    // 记录解
+    res.push([...path]);
+  }
+  preOrder(root.left, path, res);
+  preOrder(root.right, path, res);
+  // 回退
+  path.pop();
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 前序遍历
+const path = [];
+const res = [];
+preOrder(root, path, res);
+
+console.log("\n输出所有根节点到节点 7 的路径，且路径中不包含值为 3 的节点");
+res.forEach(path => {
+  console.log(path.map(node => node.val));
+});

codes/javascript/chapter_backtracking/preorder_traversal_iii_template.js

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+/**
+ * File: preorder_traversal_iii_template.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* 判断当前状态是否为解 */
+function isSolution(state) {
+  return state && state[state.length - 1]?.val === 7;
+}
+
+/* 记录解 */
+function recordSolution(state, res) {
+  res.push([...state]);
+}
+
+/* 判断在当前状态下，该选择是否合法 */
+function isValid(state, choice) {
+  return choice !== null && choice.val !== 3;
+}
+
+/* 更新状态 */
+function makeChoice(state, choice) {
+  state.push(choice);
+}
+
+/* 恢复状态 */
+function undoChoice(state) {
+  state.pop();
+}
+
+/* 回溯算法：例题三 */
+function backtrack(state, choices, res) {
+  // 检查是否为解
+  if (isSolution(state)) {
+    // 记录解
+    recordSolution(state, res);
+    return;
+  }
+  // 遍历所有选择
+  for (const choice of choices) {
+    // 剪枝：检查选择是否合法
+    if (isValid(state, choice)) {
+      // 尝试：做出选择，更新状态
+      makeChoice(state, choice);
+      // 进行下一轮选择
+      backtrack(state, [choice.left, choice.right], res);
+      // 回退：撤销选择，恢复到之前的状态
+      undoChoice(state);
+    }
+  }
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 回溯算法
+const res = [];
+backtrack([], [root], res);
+
+console.log("\n输出所有根节点到节点 7 的路径，要求路径中不包含值为 3 的节点");
+res.forEach(path => {
+  console.log(path.map(node => node.val));
+});

codes/typescript/chapter_backtracking/preorder_traversal_i_compact.ts

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+/**
+ * File: preorder_traversal_i_compact.ts
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+import { type TreeNode } from '../modules/TreeNode';
+import { arrToTree } from '../modules/TreeNode';
+import { printTree } from '../modules/PrintUtil';
+
+/* 前序遍历：例题一 */
+function preOrder(root: TreeNode | null, res: TreeNode[]): void {
+  if (root === null) {
+    return;
+  }
+  if (root.val === 7) {
+    // 记录解
+    res.push(root);
+  }
+  preOrder(root.left, res);
+  preOrder(root.right, res);
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 前序遍历
+const res: TreeNode[] = [];
+preOrder(root, res);
+
+console.log("\n输出所有值为 7 的节点");
+console.log(res.map(node => node.val));

codes/typescript/chapter_backtracking/preorder_traversal_ii_compact.ts

@@ -0,0 +1,41 @@
+/**
+ * File: preorder_traversal_ii_compact.ts
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+import { type TreeNode } from '../modules/TreeNode';
+import { arrToTree } from '../modules/TreeNode';
+import { printTree } from '../modules/PrintUtil';
+
+/* 前序遍历：例题二 */
+function preOrder(root: TreeNode | null, path: TreeNode[], res: TreeNode[][]): void {
+  if (root === null) {
+    return;
+  }
+  // 尝试
+  path.push(root);
+  if (root.val === 7) {
+    // 记录解
+    res.push([...path]);
+  }
+  preOrder(root.left, path, res);
+  preOrder(root.right, path, res);
+  // 回退
+  path.pop();
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 前序遍历
+const path: TreeNode[] = [];
+const res: TreeNode[][] = [];
+preOrder(root, path, res);
+
+console.log("\n输出所有根节点到节点 7 的路径");
+res.forEach(path => {
+  console.log(path.map(node => node.val));
+});

codes/typescript/chapter_backtracking/preorder_traversal_iii_compact.ts

@@ -0,0 +1,42 @@
+/**
+ * File: preorder_traversal_iii_compact.ts
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+import { type TreeNode } from '../modules/TreeNode';
+import { arrToTree } from '../modules/TreeNode';
+import { printTree } from '../modules/PrintUtil';
+
+/* 前序遍历：例题三 */
+function preOrder(root: TreeNode | null, path: TreeNode[], res: TreeNode[][]): void {
+  // 剪枝
+  if (root === null || root.val === 3) {
+    return;
+  }
+  // 尝试
+  path.push(root);
+  if (root.val === 7) {
+    // 记录解
+    res.push([...path]);
+  }
+  preOrder(root.left, path, res);
+  preOrder(root.right, path, res);
+  // 回退
+  path.pop();
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 前序遍历
+const path: TreeNode[] = [];
+const res: TreeNode[][] = [];
+preOrder(root, path, res);
+
+console.log("\n输出所有根节点到节点 7 的路径，且路径中不包含值为 3 的节点");
+res.forEach(path => {
+  console.log(path.map(node => node.val));
+});

codes/typescript/chapter_backtracking/preorder_traversal_iii_template.ts

@@ -0,0 +1,70 @@
+/**
+ * File: preorder_traversal_iii_template.ts
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+import { type TreeNode } from '../modules/TreeNode';
+import { arrToTree } from '../modules/TreeNode';
+import { printTree } from '../modules/PrintUtil';
+
+/* 判断当前状态是否为解 */
+function isSolution(state: TreeNode[]): boolean {
+  return state && state[state.length - 1]?.val === 7;
+}
+
+/* 记录解 */
+function recordSolution(state: TreeNode[], res: TreeNode[][]): void {
+  res.push([...state]);
+}
+
+/* 判断在当前状态下，该选择是否合法 */
+function isValid(state: TreeNode[], choice: TreeNode): boolean {
+  return choice !== null && choice.val !== 3;
+}
+
+/* 更新状态 */
+function makeChoice(state: TreeNode[], choice: TreeNode): void {
+  state.push(choice);
+}
+
+/* 恢复状态 */
+function undoChoice(state: TreeNode[]): void {
+  state.pop();
+}
+
+/* 回溯算法：例题三 */
+function backtrack(state: TreeNode[], choices: TreeNode[], res: TreeNode[][]): void {
+  // 检查是否为解
+  if (isSolution(state)) {
+    // 记录解
+    recordSolution(state, res);
+    return;
+  }
+  // 遍历所有选择
+  for (const choice of choices) {
+    // 剪枝：检查选择是否合法
+    if (isValid(state, choice)) {
+      // 尝试：做出选择，更新状态
+      makeChoice(state, choice);
+      // 进行下一轮选择
+      backtrack(state, [choice.left, choice.right], res);
+      // 回退：撤销选择，恢复到之前的状态
+      undoChoice(state);
+    }
+  }
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log("\n初始化二叉树");
+printTree(root);
+
+// 回溯算法
+const res: TreeNode[][] = [];
+backtrack([], [root], res);
+
+console.log("\n输出所有根节点到节点 7 的路径，要求路径中不包含值为 3 的节点");
+res.forEach(path => {
+  console.log(path.map(node => node.val));
+});