◼ 翻转二叉树
https://leetcode-cn.com/problems/invert-binary-tree/

◼ 计算二叉树的高度
https://leetcode-cn.com/problems/er-cha-shu-de-shen-du-lcof/

◼ 二叉树的前序遍历：
https://leetcode-cn.com/problems/binary-tree-preorder-traversal/ （递归+迭代）

◼ 二叉树的中序遍历：
https://leetcode-cn.com/problems/binary-tree-inorder-traversal/ （递归+迭代）

◼ 二叉树的后序遍历：
https://leetcode-cn.com/problems/binary-tree-postorder-traversal/ （递归+迭代）

◼ 二叉树的层次遍历：
https://leetcode-cn.com/problems/binary-tree-level-order-traversal/ （迭代）

◼ 二叉树的最大深度：
https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/ （递归+迭代）

◼ 二叉树的层次遍历II：
https://leetcode-cn.com/problems/binary-tree-level-order-traversal-ii/

◼ 二叉树最大宽度：
https://leetcode-cn.com/problems/maximum-width-of-binary-tree/

◼ N叉树的前序遍历：
https://leetcode-cn.com/problems/n-ary-tree-preorder-traversal/

◼ N叉树的后序遍历：
https://leetcode-cn.com/problems/n-ary-tree-postorder-traversal/

◼ N叉树的最大深度：
https://leetcode-cn.com/problems/maximum-depth-of-n-ary-tree/

◼ 二叉树展开为链表
https://leetcode-cn.com/problems/flatten-binary-tree-to-linked-list/

◼ 从中序与后序遍历序列构造二叉树
https://leetcode-cn.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/

◼ 从前序与中序遍历序列构造二叉树
https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/

◼ 根据前序和后序遍历构造二叉树
https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-postorder-traversal/

◼ 对称二叉树
https://leetcode-cn.com/problems/symmetric-tree/