每日一练 | Data Scientist & Business Analyst & Leetcode 面试题 725

Data Application Lab 自2017年6月15日起，每天和你分享讨论一道数据科学(DS)和商业分析(BA) 领域常见的面试问题。

自2017年10月4日起，每天再为大家分享一道Leetcode 算法题。

DS Interview Question

Tell me some majors issues needed to be considered in supervised machine learning?

BA Interview Question

Employees Earning More Than Their Managers

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 | Email   |
+----+---------+
| 1  | [email protected] |
| 2  | [email protected] |
| 3  | [email protected] |
+----+---------+

Given the Employee table, write a SQL query that finds out employees who earn more than their managers. For the above table, Joe is the only employee who earns more than his manager.

+---------+
| Email   |
+---------+
| [email protected] |
+---------+

LeetCode Question

Length of Last Word

Description:

Given a string s consists of upper/lower-case alphabets and empty space characters ’ ', return the length of last word in the string.

Input: s = “Hello World”

Output: 5

Assumptions:

If the last word does not exist, return 0.

DS Interview Question & Answer

How does a tree decide where to split?

The decision criteria is different for classification and regression trees.

Decision trees use multiple algorithms to decide to split a node in two or more sub-nodes. The creation of sub-nodes increases the homogeneity of resultant sub-nodes. Decision tree splits the nodes on all available variables and then selects the split which results in most homogeneous sub-nodes. Some most commonly used algorithms to split the node are: Gini Index, Chi-Square, Information Gain, Reduction in Variance.

BA Interview Question & Answer

Consecutive Numbers

Write a SQL query to find all numbers that appear at least three times consecutively.
+----+-----+
| Id | Num |
+----+-----+
| 1  |  1  |
| 2  |  1  |
| 3  |  1  |
| 4  |  2  |
| 5  |  1  |
| 6  |  2  |
| 7  |  2  |
+----+-----+

For example, given the above Logs table, 1 is the only number that appears consecutively for at least three times.

+-----------------+
| ConsecutiveNums |
+-----------------+
| 1               |
+-----------------+

Answer: Using DISTINCT and WHERE clause

Select DISTINCT l1.Num as ConsecutiveNums from Logs l1, Logs l2, Logs l3
where l1.Id=l2.Id-1 and l2.Id=l3.Id-1
and l1.Num=l2.Num and l2.Num=l3.Num

Reference:

https://leetcode.com/problems/consecutive-numbers/solution/