findSubFunction.kt

     fun findSubFunctions(input: List<List<String>>, maxFunctionLength: Int, maxSubFunctions: Int): List<List<String>>? {
        if (input.isEmpty()) {
            return emptyList()
        }
        if (maxSubFunctions == 0) {
            return null
        }
        for (i in 1..input[0].size) {
            val candidate = input[0].subList(0, i)
            if (candidate.joinToString(",").length > maxFunctionLength) {
                break;
            }
            val fragments = input.flatMap { it.split(candidate) }.filter { it.isNotEmpty() }
            val res = findSubFunctions(fragments, maxFunctionLength, maxSubFunctions - 1)
            if (res != null) {
                return res.plusAt(0, candidate)
            }
        }
        return null;
    }