bug fixed

ScriptOJ/isBalanced.js

@@ -17,7 +17,7 @@ var isBalanced = function(root) {
     if(node === null) return 0;
     let left = dfs(node.left);
     let right = dfs(node.right);
-    if(Math.abs(left, right) > 1) {
+    if(Math.abs(left-right) > 1) {
       ans = false;
     }
     return Math.max(left, right) + 1;

ScriptOJ/isSymmetric.js

@@ -0,0 +1,23 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {boolean}
+ */
+var isSymmetric = function(root) {
+  if(root == null) return true;
+
+  function recur(L, R) {
+    if(L === null && R === null) return true;
+    if(L === null || R === null || L.val !== R.val) return false;
+
+    return recur(L.left, R.right) && recur(L.right, R.left);
+  }
+
+  return recur(root.left, root.right);
+};

Solutions/leetcode-solution/二叉树.md

@@ -73,3 +73,4 @@ var postorderTraversal = function(root) {
 ### 题目列表
 - [x] 112. 路径总和 https://leetcode-cn.com/problems/path-sum/
 - [x] 面试题27. 二叉树的镜像 https://leetcode-cn.com/problems/er-cha-shu-de-jing-xiang-lcof/
+- [x] 面试题28. 对称的二叉树  https://leetcode-cn.com/problems/dui-cheng-de-er-cha-shu-lcof/