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# Write a method to find number of occurrences per second and minute

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Hi,
I might be rather stupid here, but I am trying to find way to write a method that will return the number of request in a specific timeframe. The number of requests are in an Array in this form:

This means that there are 4 requests that arrive at second 1 and 2 at second 2. My approach would be to basically work out the duplicates that there are in the array (so basically saying there are 4 occurrences of 1), but then somehow I am not sure how to include the time aspect. I am really looking for some advice on the algorithm, not a proper solution.

Thank you

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Why use a List? Just use a Map with the minute as its key, and the frequency as its value. Such a mapping is called a histogram.

You can use histogram.merge(minute, 1, Integer::sum) instead of what you're doing with resFrequency.add(minute) now.

Stephan van Hulst
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If you already have a list of the key type, and you want to convert it to a histogram, you can convert the list to a Stream and then call Stream.collect() using Collectors.groupingBy() and Collectors.counting().

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