Hash maps

Average O(1) lookup, the most useful tool in coding rounds.

A hash map turns a key into a position, so lookups stay fast however much data it holds. When a question feels like O(n²), ask what you could remember in a map.

Two sum

Expected output

(0, 1)

Group anagrams

Expected output

[['eat', 'tea'], ['tan', 'nat']]

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