/*
Efficient algorithm using Kotlin Sets:
--------------------------------------
Each word is converted into a Set<Char> of its unique letters.
Example:
"algebraic" -> setOf('a','l','g','e','b','r','i','c')
Then:
- Start with the set of letters from the first word.
- Intersect with each subsequent word's letter set.
- The final set contains letters common to all words.
This uses Kotlin's built-in:
- Set<Char>
- intersect()
- map, drop, and functional decomposition
*/
// Convert a word into a Set<Char> of its unique letters
fun lettersOf(word: String): Set<Char> =
word.toSet()
// Compute letters common to all words
fun commonLetters(words: List<String>): Set<Char> {
if (words.isEmpty()) return emptySet()
// Start with letters of the first word
var common: Set<Char> = lettersOf(words.first())
// Intersect with each subsequent word
for (word in words.drop(1)) {
val current: Set<Char> = lettersOf(word)
common = common.intersect(current)
}
return common
}
// Print letters in sorted order
fun printLetters(letters: Set<Char>) {
println(letters.sorted().joinToString(" "))
}
fun main() {
val words: List<String> = listOf(
"algebraic",
"alphabetic",
"ambiance",
"abacus",
"metabolic",
"parabolic",
"playback",
"drawback",
"fabricate",
"flashback",
"syllabic"
)
val result: Set<Char> = commonLetters(words)
println("Common letters across all words:")
printLetters(result)
}
/*
run:
Common letters across all words:
a b c
*/
