add JavaScript codes for PrintUtil

codes/javascript/chapter_tree/binary_search_tree.js

@@ -5,6 +5,7 @@
  */
 
 const Tree = require("../include/TreeNode");
+const { printTree } = require("../include/PrintUtil");
 
  /* 二叉搜索树 */
 var root;
@@ -122,7 +123,7 @@ function min(root) {
 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");
-console.log(getRoot());
+printTree(getRoot());
 
 /* 查找结点 */
 let node = search(5);
@@ -131,15 +132,15 @@ console.log("\n查找到的结点对象为 " + node + "，结点值 = " + node.v
 /* 插入结点 */
 node = insert(16);
 console.log("\n插入结点 16 后，二叉树为\n");
-console.log(getRoot());
+printTree(getRoot());
 
 /* 删除结点 */
 remove(1);
 console.log("\n删除结点 1 后，二叉树为\n");
-console.log(getRoot());
+printTree(getRoot());
 remove(2);
 console.log("\n删除结点 2 后，二叉树为\n");
-console.log(getRoot());
+printTree(getRoot());
 remove(4);
 console.log("\n删除结点 4 后，二叉树为\n");
-console.log(getRoot());
+printTree(getRoot());

codes/javascript/chapter_tree/binary_tree.js

@@ -5,7 +5,8 @@
  */
 
 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),
@@ -19,7 +20,7 @@ n1.right = n3;
 n2.left = n4;
 n2.right = n5;
 console.log("\n初始化二叉树\n")
-console.log(n1)
+printTree(n1)
 
 /* 插入与删除结点 */
 let P = new Tree.TreeNode(0);
@@ -27,8 +28,8 @@ let P = new Tree.TreeNode(0);
 n1.left = P;
 P.left = n2;
 console.log("\n插入结点 P 后\n");
-console.log(n1);
+printTree(n1);
 // 删除结点 P
 n1.left = n2;
 console.log("\n删除结点 P 后\n");
-console.log(n1);
+printTree(n1);

codes/javascript/chapter_tree/binary_tree_bfs.js

@@ -4,7 +4,8 @@
  * Author: IsChristina (christinaxia77@foxmail.com)
  */
 
-let { arrToTree } = require("../include/TreeNode");
+const { arrToTree } = require("../include/TreeNode");
+const { printTree } = require("../include/PrintUtil");
 
 /* 层序遍历 */
 function hierOrder(root) {
@@ -29,7 +30,7 @@ function hierOrder(root) {
 // 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");
-console.log(root);
+printTree(root);
 
 /* 层序遍历 */
 let list = hierOrder(root);

codes/javascript/chapter_tree/binary_tree_dfs.js

@@ -4,7 +4,8 @@
  * Author: IsChristina (christinaxia77@foxmail.com)
  */
 
-let { arrToTree } = require("../include/TreeNode");
+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 = []
@@ -41,7 +42,7 @@ function postOrder(root) {
 // 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");
-console.log(root);
+printTree(root);
 
 /* 前序遍历 */
 list.length = 0;

codes/javascript/include/PrintUtil.js

@@ -0,0 +1,88 @@
+/**
+ * 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,
+}