# 归档 2015年1月

## 二叉树后序遍历的非递归实现 作者是 在线疯狂 发布于 2015年1月19日 在 数据结构.

二叉树的后序遍历很容易采用递归方式实现：

``````void postOrderTraversal(BinaryTree *p) {
if (!p) return;
postOrderTraversal(p->left);
postOrderTraversal(p->right);
cout << p->data;
}
``````

```树的删除。为了释放树结构的内存，某节点在被释放以前，其左右子树的节点首先应当被释放掉。

## 题目描述：

Given a binary tree, return the inorder traversal of its nodes' values.

```For example:
Given binary tree {1,#,2,3},
1
\
2
/
3
return [1,3,2].```

Note: Recursive solution is trivial, could you do it iteratively?

## 题目描述：

John is standing at the origin of an infinite two-dimensional grid. He is going to move along this grid. During each second he can either stay where he is or he can move by one unit in one of ...

## 题目描述：

Write a SQL query to find all duplicate emails in a table named Person.

```+----+---------+
| Id | Email   |
+----+---------+
| 1  | a@b.com |
| 2  | c@d.com |
| 3  | a@b.com |
+----+---------+
For example, your query should return the following for the above ...```

## 题目描述：

The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.

```+----+-------+--------+-----------+
| Id | Name  | Salary | ManagerId |
+----+-------+--------+-----------+
| 1  | Joe   | 70000  | 3         |
| 2  | Henry | 80000  | 4         |
| 3  | Sam   | 60000 ...```