algorithm<tree>: add reverse binary tree

Author: careteenL

assets/alg-btree-reverse-1.png

@@ -195,4 +195,16 @@ export default class BST {
       if (curNode.right) queue.enqueue(curNode.right)
     }
   }
+
+  /**
+   * @desc 反转二叉树
+   */
+  reverse (node = this.root) {
+    if (!node) return
+    const tmp = node.left
+    node.left = node.right
+    node.right = tmp
+    this.reverse(node.left)
+    this.reverse(node.right)
+  }
 }

assets/alg-btree-reverse-2.png

@@ -1,4 +1,4 @@
-export class Node {
+export default class Node {
   constructor (key) {
     this.key = key
     this.left = null

assets/alg-btree-reverse.png

@@ -0,0 +1,21 @@
+# 反转二叉树
+
+## 前言
+
+![alg-btree](../../assets/alg-btree.png)
+将上图的二叉树反转为为下图的二叉树
+![alg-btree-reverse](../../assets/alg-btree-reverse.png)
+
+## 分析
+
+![alg-btree-reverse-1](../../assets/alg-btree-reverse-1.png)
+![alg-btree-reverse-2](../../assets/alg-btree-reverse-2.png)
+
+## 实现
+
+[详细实现](./binary-search-tree.js#L202)
+[测试用例](../../test/tree.spec.js#L26)
+
+## 总结
+
+思路较为简单

assets/alg-btree.png

@@ -7,6 +7,7 @@
 - [API](#api)
 - [Usage](#usage)
 - [Where](#where)
+  - [反转二叉树](#反转二叉树)
 
 ### What
 
@@ -148,7 +149,9 @@ to be replaced
 
 ### Where
 
-to be replaced
+#### 反转二叉树
+
+- [详见](./tree-reverse.md)
 
-- 更多使用场景...
+#### 更多使用场景...
 

src/data-structure/binary-search-tree.js

@@ -0,0 +1,45 @@
+
+import 'mocha'
+import { expect } from 'chai'
+
+import BST from '../src/data-structure/binary-search-tree.js'
+
+describe('BST', () => {
+  it('BST: inOrderTraverse', () => {
+    let bst = new BST()
+    bst.insert(1)
+    bst.insert(5)
+    bst.insert(9)
+    bst.insert(4)
+    bst.insert(2)
+    bst.insert(7)
+    bst.insert(3)
+    bst.insert(8)
+    let orderList = []
+    bst.inOrderTraverse((key) => {
+      orderList.push(key)
+    })
+    // console.log(orderList)
+    expect(orderList).to.eql([ 1, 2, 3, 4, 5, 7, 8, 9 ])
+  })
+  
+  it('BST: reverse inOrderTraverse', () => {
+    let bst = new BST()
+    bst.insert(1)
+    bst.insert(5)
+    bst.insert(9)
+    bst.insert(4)
+    bst.insert(2)
+    bst.insert(7)
+    bst.insert(3)
+    bst.insert(8)
+  
+    bst.reverse()
+    let reverseOrderList = []
+    bst.inOrderTraverse((key) => {
+      reverseOrderList.push(key)
+    })    
+    // console.log(reverseOrderList)
+    expect(reverseOrderList).to.eql([ 9, 8, 7, 5, 4, 3, 2, 1 ])
+  })
+})