Top k most frequent elements

Medium25 minFree, no account

Sorting works. The question is whether you can beat it, and whether you know when not to bother.

The question

Given an array and a number k, return the k most frequent elements.

Give the complexity of your approach, and say what you would do if the array did not fit in memory.

topK([1,1,1,2,2,3], 2)        // [1, 2]
topK(["a","b","a","c","b","a"], 1)  // ["a"]

25:00Commit to an answer before you open the solution. Reading it first teaches you to recognise good answers, which is not the skill being tested.

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The worked solution

written by a person · not a grade

Score yourself

0 of 5 marked

Correct counting and a working top-k25
Gave more than one approach with honest complexities25
Produced the O(n) bucket solution and stated its precondition25
Distinguished n from m in the analysis15
Had an answer for data that does not fit in memory10

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