Next Q: Is there a more idiomatic way to find firs...

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[arnab]

Next Q: Is there a more idiomatic way to find first duplicate in a List

What I have creates a mutableList of counts and then picks the first one by `count > 1`:

fun <E> List<E>.findFirstDuplicate(): E? {
    val counts = mutableMapOf<E, Int>()
    this.forEach {
        if (counts.containsKey(it))
            counts.put(it, counts[it]!! + 1)
        else
            counts.put(it, 1)
    }

    return this.find { counts[it]!! > 1 }
}