每日一练 | Data Scientist & Business Analyst & Leetcode 面试题 327
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 227
DS Interview Questions
What is the Box-Cox transformation used for?
BA Interview Questions
Given a vector:
a = c(1, 5, 4,"yes",0)
What's the result of class(a)?
LeetCode Questions
Given a set of candidate numbers © (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.
The same repeated number may be chosen from C unlimited number of times.
Input: [2, 3, 6, 7]
Output: [[7], [2, 2, 3]]
Assumptions:
without duplicates
All numbers (including target) will be positive integers.
Description:
欲知答案如何？请见下期分解！
Day 226 答案揭晓
DS Interview Questions
What is the difference between stochastic gradient descent (SGD) and gradient descent (GD)?
Both algorithms are methods for finding a set of parameters that minimize a loss function by evaluating parameters against data and then making adjustments.
In standard gradient descent, you'll evaluate all training samples for each set of parameters. This is going to take big, slow steps toward the solution.
In stochastic gradient descent, you'll evaluate only a certain part of training samples for the set of parameters before updating them. This is going to take small, quick steps toward the solution.
BA Interview Questions
R Programming: What are six types of atomic vector?
raw，Integer, double, complex, character and logical
LeetCode Questions
The count-and-say sequence is the sequence of integers with the first five terms as following:
1 is read off as “one 1” or 11.
11 is read off as “two 1s” or 21.
21 is read off as “one 2, then one 1” or 1211.
Given an integer n, generate the nth term of the count-and-say sequence.
Note: Each term of the sequence of integers will be represented as a string.
Description:
Input: 4
Output: “1211”
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