每日一练 | Data Scientist & Business Analyst & Leetcode 面试题 314

大数据应用 · 公众号 · 大数据 · 2018-03-16 09:00

正文

自2017年6月15日起，数据应用学院与你一起温习数据科学（DS）和商业分析（BA）领域常见的面试问题。从2017年10月4号起，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。

Day 214

DS Interview Questions

What is random forest? Why is it good?

BA Interview Questions

What is B2B,B2C,C2C,C2B in E-Commerce Industry?

LeetCode Questions

Description:

Given a string containing just the characters ‘(’, ‘)’, ‘{’, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.
The brackets must close in the correct order, “()” and “()[]{}” are all valid but “(]” and “([)]” are not.

Input: “()[]{}”

Output: true

欲知答案如何？请见下期分解！

Day 213 答案揭晓

DS Interview Questions

Is orthogonal necessary in PCA? If yes, Why? What will happen if you don’t rotate the components?

Yes, because in PCA, we aim to select fewer components (than features) which can explain the maximum variance in the data set, and by doing orthogonal it will maximize the difference between variance captured by the component.

If we don’t rotate the components, the effect of PCA will diminish and we’ll have to select more number of components to explain variance in the data set.

BA Interview Questions

R language

write a for() loop that uses next to print all values except “3” in the following variable:

for (a in i){

if(a==3) next;

print(a)

}

Leetcode Questions

Description:

Given a digit string, return all possible letter combinations that the number could represent.
A mapping ofdigitto letters (just like on the telephone buttons) is given below.