专栏名称: 大数据应用

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每日一练 | Data Scientist & Business Analyst & Leetcode 面试题 937

大数据应用 · 公众号 · 大数据 · 2020-08-19 09:50

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点击上方蓝字会变美

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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。

希望积极寻求相关领域工作的你每天关注我们的问题并且与我们一起思考，我们将会在第二天给出答案。

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DS Interview Question

What is Principal Component Analysis? What are its applications and limitations?

BA Interview Question

Write a query in SQL to make a report which will show

a) name of the patient

b) name of the physician who is treating him or her

c) name of the nurse who is attending him or her

d) which treatment is going on to the patient

e) the date of release

f) in which room the patient has admitted and which floor and block the room belongs to respectively

LeetCode Question

Remove Element

Description:

Given an array and a value, remove all instances of that value in place and return the new length.

Do not allocate extra space for another array, you must do this in place with constant memory.

The order of elements can be changed. It doesn’t matter what you leave beyond the new length.

Input: [3,2,2,3]

Output: 2

Assumptions:

Do not allocate extra space for another array, you must do this in place with constant memory.

Day

836

答案揭晓

DS Interview Question & Answer

Explain what resampling methods are and why they are useful.

Resampling methods involve:

Repeatedly drawing a sample from the training data;

Refitting the model of interest with each new sample;

Examining all the refitted models and then drawing conclusions.

There are two major resampling techniques: cross-validation and bootstrapping, both are easy to implement and and broadly applicable. Cross-validation is used for model assessment and model selection, while bootstrapping is most commonly used to measure the accuracy of a parameter estimate of a given learning model.

Resampling methods are useful because they can address the following drawbacks of traditional validation-test approach:

data are often scarce and we cannot afford to set aside a validation or test set when training a model;

the model performance on the validation data is highly dependent on how we split the data, and validation error tends to overestimate the test error rate.

BA Interview Question & Answer

Write a query in SQL to obtain the nurses and the block where they are booked for attending the patients on call

Sample table: nurse

employeeid | name | position | registered | ssn
---------------+-----------------------+------------------+---------------+-----------
101 | Carla Espinosa | Head Nurse | t | 111111110
102 | Laverne Roberts | Nurse | t | 222222220
103 | Paul Flowers | Nurse | f | 333333330

Answer:

SELECT n.name AS "Nurse",
o.blockcode AS "Block"
FROM nurse n
JOIN on_call o ON o.nurse=n.employeeid;

Sample Output:

每日一练 | Data Scientist &amp; Business Analyst &amp; Leetcode 面试题 937

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每日一练 | Data Scientist & Business Analyst & Leetcode 面试题 937