Add and Update the module TypeScript code (Chapter of Tree)

codes/typescript/module/PrintUtil.ts

@@ -1,11 +1,26 @@
 /*
  * File: PrintUtil.ts
- * Created Time: 2022-12-10
+ * Created Time: 2022-12-13
  * Author: Justin (xiefahit@gmail.com)
  */
 
 import ListNode from './ListNode';
+import { TreeNode } from './TreeNode';
 
+class Trunk {
+    prev: Trunk | null;
+    str: string;
+
+    constructor(prev: Trunk | null, str: string) {
+        this.prev = prev;
+        this.str = str;
+    }
+}
+
+/**
+ * Print a linked list
+ * @param head
+ */
 function printLinkedList(head: ListNode | null): void {
     const list: string[] = [];
     while (head !== null) {
@@ -15,4 +30,67 @@ function printLinkedList(head: ListNode | null): void {
     console.log(list.join(' -> '));
 }
 
-export { printLinkedList };
+/**
+ * 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: TreeNode | null) {
+    printTreeHelper(root, null, false);
+}
+
+/**
+ * Print a binary tree
+ * @param root
+ * @param prev
+ * @param isLeft
+ */
+function printTreeHelper(root: TreeNode | null, prev: Trunk | null, isLeft: boolean) {
+    if (root === null) {
+        return;
+    }
+
+    let prev_str = '    ';
+    const trunk = new Trunk(prev, prev_str);
+
+    printTreeHelper(root.right, trunk, true);
+
+    if (prev === null) {
+        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 = '   |';
+
+    printTreeHelper(root.left, trunk, false);
+}
+
+/**
+ * Helper function to print branches of the binary tree
+ * @param p
+ */
+function showTrunks(p: Trunk | null) {
+    if (p === null) {
+        return;
+    }
+
+    showTrunks(p.prev);
+    process.stdout.write(p.str);
+    // ts-node to execute, we need to install type definitions for node
+    // solve: npm i --save-dev @types/node
+    // restart the vscode
+}
+
+export { printLinkedList, printTree };

codes/typescript/module/TreeNode.ts

@@ -0,0 +1,51 @@
+/*
+ * File: TreeNode.ts
+ * Created Time: 2022-12-13
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/**
+ * Definition for a binary tree node.
+ */
+class TreeNode {
+    val: number;
+    left: TreeNode | null;
+    right: TreeNode | null;
+
+    constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+        this.val = val === undefined ? 0 : val; // 结点值
+        this.left = left === undefined ? null : left; // 左子结点指针
+        this.right = right === undefined ? null : right; // 右子结点指针
+    }
+}
+
+/**
+ * Generate a binary tree with an array
+ * @param arr
+ * @return
+ */
+function arrToTree(arr: (number | null)[]): TreeNode | null {
+    if (arr.length === 0) {
+        return null;
+    }
+
+    const root = new TreeNode(arr[0] as number);
+    const queue = [root];
+    let i = 1;
+    while (queue.length) {
+        let node = queue.shift() as TreeNode;
+        if (arr[i] !== null) {
+            node.left = new TreeNode(arr[i] as number);
+            queue.push(node.left);
+        }
+        i++;
+        if (arr[i] !== null) {
+            node.right = new TreeNode(arr[i] as number);
+            queue.push(node.right);
+        }
+        i++;
+    }
+    return root;
+}
+
+export { TreeNode, arrToTree };