Interview Cake
Counting is a common pattern in time-saving algorithms. It can often get you runtime, but at the expense of adding space.
The idea is to define a hash map or array (call it e.g. counts) where the keys/indices represent the items from the input set and the values represent the number of times the item appears. In one pass through the input you can fully populate counts:
Once you know how many times each item appears, it's trivial to:
- generate a sorted array
- find the item that appears the most times
- etc.
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