Amazon Online Assessment 2021 (OA) - Class Grouping

Amazon Technical Academy (ATA) provides in-demand, technical training to current Amazon employees looking to broaden their skill sets. ATA has admitted a group of n prospective trainees with varying skill levels. To better accommodate the trainees, ATA has decided to create classes tailored to the skill levels. A placement examination will return a skill level that will be used to group the trainees into classes, where levels[i] represents the skill level of trainee i. All trainees within a class must have a skill level within maxSpread, a specified range of one another. Determine the minimum number of classes that must be formed.

This problem is same as Group division.

Relevant Amazon OA Problems:


  • levels: the skill level for each student
  • max_spread: the maximum allowed skill difference between any two class members of a class


the minimum number of classes that can be formed


Example 1:


1levels = [1, 4, 7, 3, 4]
2max_spread = 2

Output: 3


The trainee must be within maxSpread = 2 levels of each other. In this case, one optimal grouping is {1, 3}, {4, 4}, and {7}. Another possible grouping is {1}, {3, 4, 4}, {7}. There is no way to form fewer than 3 classes.


  • 1<=n<=10^5
  • 1<=level[i]<=10^9
  • 0<=maxSpread<=10^9

Try it yourself




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1  >>> a = [1, 2, 3]
2  >>> a[-1]
3  3

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