[LeetCode] Invert Binary Tree

LeetCode 102. 二叉树的层序遍历 Binary Tree Level Order Traversal LeetCode 102. 二叉树的层序遍历 Binary Tree Level Order Traversal
LeetCode 110. Balanced Binary Tree 给定一颗二叉树，判断此树是不是平衡二叉树. 平衡二叉树的条件是：当前节点的左右子树高度差不超过1，且左右子树都是平衡二叉树.
# Leetcode 67：Add Binary(二进制求和) Leetcode 67：Add Binary(二进制求和) (python、java) Given two binary strings, return their sum (also a binary string). The input strings are both non-empty and contains only characters 1 or 0. 给定两个二进制字符串，返回他们的和（用二进制表示）。