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  1. Practice
  2. Data Structures
  3. Arrays
  4. Sparse Arrays
  5. Discussions

Sparse Arrays

  • solomkinmv + 2 comments

    Your solution is very inefficient.

    Here I suggest you functional approach, better efficiency and readability.

    Scanner sc = new Scanner(System.in);

Map<String, Long> counterMap = Stream.generate(sc::next)
    .limit(sc.nextInt())
    .collect(groupingBy(identity(), counting()));

Stream.generate(sc::next)
    .limit(sc.nextInt())
    .map(query -> counterMap.getOrDefault(query, 0L))
    .forEach(System.out::println);

    P.S. imports are omitted.

    • raggzy + 0 comments

      Nice 3-liner for HashMap solution, upvoting!

    • bah_konu + 1 comment

      Can you explain this solution please? Thanks

      • solomkinmv + 0 comments
        Stream.generate(sc::next)
    .limit(sc.nextInt())

        Reads first N words, where N is the result of sc.nextInt().

        .collect(groupingBy(identity(), counting()))

        Creates map of word occurences. This collector groups all words by it's identity (the word itself becomes key) and then the number of words becomes value.

        The second stream contains queries. 

        .map(query -> counterMap.getOrDefault(query, 0L))

        Then I transform each query to the appropriate count result by accessing map of counters. If there is no such key in the map then I use 0 as the default value.

        .forEach(System.out::println)

        Finally, I print all values.