import java.util.HashMap
fun removeOddFrequencyCharacters(s: String): String {
val frequencyMap = HashMap<Char, Int>()
val chArray = s.toCharArray()
// Count the frequency of each character
for (ch in chArray) {
frequencyMap[ch] = frequencyMap.getOrDefault(ch, 0) + 1
}
// Build the result string excluding characters with odd frequencies
val result = StringBuilder()
for (ch in chArray) {
if (frequencyMap[ch]!! % 2 == 0) {
result.append(ch)
}
}
return result.toString()
}
fun main() {
var s = "kotlin programming version 2.0.20"
s = removeOddFrequencyCharacters(s)
println(s)
}
/*
run:
gmmg2.0.20
*/