Terrible oh-so-functional Java

description.md

Tried to make an as convoluted as I possibly can "functional" solution in Java to this problem: https://twitter.com/Al_Grigor/status/1357028887209902088

I would not have made the 25 minute limit and fail to get the job, and on my way home would probably also beat myself up for not just using a damn for-loop.

Fun exercise none the less.

EqualConsecutiveItemsCounts.java

record Count<T>(T item, int count) {
    List<Count<T>> sumIf(BiPredicate<? super T, ? super T> shouldSum, Count<T> other) {
        return shouldSum.test(item, other.item) ? List.of(new Count<>(item, count + other.count)) : List.of(this, other);
    }
    @Override
    public String toString() {
        return "(\"" + item + "\"," + count + ")";
    }
}

var equalConsecutiveCharsCounts =
        "aaaabbbcca".chars()
        .mapToObj(c -> new Count<>((char) c, 1))
        .collect(LinkedList<Count<Character>>::new,
                (counts, count) -> Optional.ofNullable(counts.pollLast())
                    .map(lastCount -> lastCount.sumIf(Objects::equals, count))
                    .ifPresentOrElse(counts::addAll, () -> counts.add(count)),
                List<Count<Character>>::addAll);

System.out.println(equalConsecutiveCharsCounts); // [("a",4), ("b",3), ("c",2), ("a",1)]