From 74cb27fa2c8106fbcd6a25344ae474f81078f198 Mon Sep 17 00:00:00 2001
From: Junwen Huang <hjwbelieve@gmail.com>
Date: Sat, 23 Oct 2021 20:47:43 +0800
Subject: [PATCH] =?UTF-8?q?Update=200106.=E4=BB=8E=E4=B8=AD=E5=BA=8F?=
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优化js版本代码并添加注释说明
---
 ...序与后序遍历序列构造二叉树.md | 31 +++++++++----------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/problems/0106.从中序与后序遍历序列构造二叉树.md b/problems/0106.从中序与后序遍历序列构造二叉树.md
index a83341fd..11083a59 100644
--- a/problems/0106.从中序与后序遍历序列构造二叉树.md
+++ b/problems/0106.从中序与后序遍历序列构造二叉树.md
@@ -792,16 +792,13 @@ func findRootIndex(target int,inorder []int) int{
 
 ```javascript
 var buildTree = function(inorder, postorder) {
-    if (!postorder.length) return null
-    
-    let root = new TreeNode(postorder[postorder.length - 1])
-    
-    let index = inorder.findIndex(number => number === root.val)
-    
-    root.left = buildTree(inorder.slice(0, index), postorder.slice(0, index))
-    root.right = buildTree(inorder.slice(index + 1, inorder.length), postorder.slice(index, postorder.length - 1))
-    
-    return root
+    if (!preorder.length) return null;
+    const rootVal = postorder.pop(); // 从后序遍历的数组中获取中间节点的值， 即数组最后一个值
+    let rootIndex = inorder.indexOf(rootVal); // 获取中间节点在中序遍历中的下标
+    const root = new TreeNode(rootVal); // 创建中间节点
+    root.left = buildTree(inorder.slice(0, rootIndex), postorder.slice(0, rootIndex)); // 创建左节点
+    root.right = buildTree(inorder.slice(rootIndex + 1), postorder.slice(rootIndex)); // 创建右节点
+    return root;
 };
 ```
 
@@ -809,13 +806,13 @@ var buildTree = function(inorder, postorder) {
 
 ```javascript
 var buildTree = function(preorder, inorder) {
-    if(!preorder.length)
-        return null;
-    let root = new TreeNode(preorder[0]);
-    let mid = inorder.findIndex((number) => number === root.val);
-    root.left = buildTree(preorder.slice(1, mid + 1), inorder.slice(0, mid));
-    root.right = buildTree(preorder.slice(mid + 1, preorder.length), inorder.slice(mid + 1, inorder.length));
-    return root;
+  if (!preorder.length) return null;
+  const rootVal = preorder.shift(); // 从前序遍历的数组中获取中间节点的值， 即数组第一个值
+  const index = inorder.indexOf(rootVal); // 获取中间节点在中序遍历中的下标
+  const root = new TreeNode(rootVal); // 创建中间节点
+  root.left = buildTree(preorder.slice(0, index), inorder.slice(0, index)); // 创建左节点
+  root.right = buildTree(preorder.slice(index), inorder.slice(index + 1)); // 创建右节点
+  return root;
 };
 ```