题目描述：
Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything.
Table: Customers.
+----+-------+ | Id | Name | +----+-------+ | 1 | Joe ...
类别归档：LeetCode
LeetCode OJ is a platform for preparing technical coding interviews.
[LeetCode]Customers Who Never Order
[LeetCode]Binary Tree Postorder Traversal
作者是
发布于
在
LeetCode.
题目描述：
Given a binary tree, return the postorder traversal of its nodes' values.
For example:
Given binary tree {1,#,2,3},
1
\
2
/
3
return [3,2,1].
Note: Recursive solution is trivial, could you do it iteratively?
题目大意：
非递归实现二叉树的后序遍历
解题思路：
参考博文： ...
[LeetCode]Binary Tree Inorder Traversal
作者是
发布于
在
LeetCode.
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?
题目大意：
非递归实现二叉树的中序遍历
解题思路：
使用栈（Stack） ...
[LeetCode]Duplicate Emails
作者是
发布于
在
LeetCode.
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, ...
[LeetCode]Employees Earning More Than Their Managers
作者是
发布于
在
LeetCode.
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 ...