Hash Maps and Counting

A hash map turns a search into a lookup, and the three problems below all lean on that. Two come from one onsite round where the interviewer kept changing the rules on the same bag of integers. The third comes from a phone screen.

Decide what the map holds before you write code. After that, each solution is a loop over keys or over pairs. Progressive rounds like this one reward code that's easy to change. When the rule moves, you want to change one condition and keep the rest of the loop. Keep the counting separate from the rule you check, and the second answer comes quickly.

WaymoPremium lesson · Coding round

The 3 Waymo problems are below.

1. 1A Premium questionCoding · Medium
2. 2A Premium questionCoding · Medium
3. 3A Premium questionCoding · Medium

Each with hints, the follow-up and a tested solution.

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