Frequency count [mp]

Micro pattern¶

Description¶

Count occurrences of values or derived keys for matching, ranking, or aggregation.

Problems¶

Value frequencies¶

Build a frequency table for characters, numbers, or tasks.

• 242. Valid Anagram (Top Easy)
• 350. Intersection of Two Arrays II (Top Easy)
• 387. First Unique Character in a String (Top Easy)
• 347. Top K Frequent Elements (Top Medium)
• 1002. Find Common Characters (Google Prep)
• 621. Task Scheduler (Top Medium)
• 315. Count of Smaller Numbers After Self (Top Hard)
• 740. Delete and Earn (Dynamic Programming)

Window frequencies¶

Increment counts entering a window and decrement counts leaving it.

• 904. Fruit Into Baskets (Google Prep)
• 76. Minimum Window Substring (Top Hard)

Derived-key frequencies¶

Count derived aggregates or properties instead of original values.

• 454. 4Sum II (Top Hard)
• 149. Max Points on a Line (Top Hard)
• 1857. Largest Color Value in a Directed Graph (Graph Theory)