n-th frequent letter (with stubs)

nthfrequent1.kt

/** Given a string return the index of the first apperance of the n-th most frequent letter
 * If two letters are equally frequent return the matching index of any of the the two
 * Examples: "aabbbc" , 3 will return 5 , "aabbbbc", 1 will return 2
 */

fun firstIndexOfNthMostFrequentChar(str: String, n: Int): Int {
    val countsMap = createCountsMap(str)
    if (countsMap.size < n) {
        return -1
    }
    
    val sortedKeyValuePairs = sortKeyValuePairs(countsMap)
    val ch = sortedKeyValuePairs[n-1].first
    return str.indexOf(char = ch, startIndex = 0)
}

fun sortKeyValuePairs(map: Map<Char, Int>): List<Pair<Char, Int>> {
    return listOf()
}

fun createCountsMap(str: String): Map<Char, Int> {
    return mapOf()
}