3 articles
Sort an array by element frequency ascending (ties broken by value descending) using a frequency map and custom comparator — a clean problem that tests mastery of custom sort keys.
Find the minimum number of distinct values to remove to halve the array size by greedily eliminating the most frequent elements first — a clean greedy problem with a frequency max-heap.
Group anagrams, find anagram occurrences, and detect anagrams under constraints. Master the three classical encodings — sorted key, 26-bucket frequency vector, and prime-product hash — with rolling-window extensions used at Meta and Google.