Make all combinations of size k

combo.kt

fun comboOfSizeK(word: String, r: Int): List<String> {
    val list = arrayListOf<String>()

    fun comobs(word: String, created: String, start: Int, end: Int, sizeOfCombo: Int) {
        if (created.length == sizeOfCombo) {
            list.add(created)
            return
        }

        if (start > end) {
            return
        }

        for(i in start..end) {
            comobs(word,created + word[i], i+1, end, sizeOfCombo)
        }
    }

    comobs(word, "", 0, word.length - 1, r)
    return list
}