Subwords.kt

import java.io.File

val dictionary    = "/usr/share/dict/words"
val minimumLength = 5

fun main(args: Array<String>) {
    val words  = File(dictionary).readLines()
    val output = File("/Users/william/Desktop/words.txt").bufferedWriter()

    words.forEach { word ->
        val wordsThatContainWord = wordsContaingWord(words, word)
        if (wordsThatContainWord.isNotEmpty()) {
            val formattedWords = wordsThatContainWord.joinToString(", ")
            output.write("${word}: ${formattedWords}\n")
        }
    }
}

fun wordsContaingWord(words: List<String>, word: String): List<String> {
    val wordLowerCase = word.toLowerCase()
    return words.filter { wordInDictionary ->
        val wordInDictionaryLowerCase = wordInDictionary.toLowerCase()
        wordInDictionaryLowerCase.contains(wordLowerCase)
                && wordInDictionaryLowerCase != wordLowerCase
                && wordLowerCase.count() >= minimumLength
    }
}