每日一练 | Data Scientist & Business Analyst & Leetcode 面试题 324

Day 224

You are working on a time series data set. You manager has asked you to build a high accuracy model. You start with the decision tree algorithm, since you know it works fairly well on all kinds of data. Later, you tried a time series regression model and got higher accuracy than decision tree model. Can this happen? Why?

Why do you think LTV and ‘cost per install’ (CPI) are important in the mobile gaming industry?

• Description:

• Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

• Input: [1,3,5,6], 5

• Output: 2

• Assumptions:

• assume no duplicates in the array.

Day 223 答案揭晓

What’s the difference between a generative and discriminative model?

A generative model will learn categories of data while a discriminative model will simply learn the distinction between different categories of data. Discriminative models will generally outperform generative models on classification tasks.

Reference:

https://stackoverflow.com/questions/879432/what-is-the-difference-between-a-generative-and-discriminative-algorithm

What is the meaning of ‘lifetime value’ (LTV)? What LTV can tell you?

Answer:

Lifetime value is the revenue that a customer will generated for your mobile game during their lifetime, but we cannot sure how long his/her lifetime in this game will be, so we make it as a predicted periodic value.

LTV could be a sign of your business health’s success, a measure of customer’s loyalty and it could also be used for forecasting growth; Moreover, it could determine our marketing budget, it tells you how much you can pay to acquire a customer.

• Description:

• Given an array of integers sorted in ascending order, find the starting and ending position of a given target value.

• Your algorithm’s runtime complexity must be in the order of O(log n).