Les palindromes

fun isPalindrome (s: String): Boolean {
    for (i in 0 until s.length / 2) {
        if (s[i] != s[s.length - i -1]) {
            return false
        }
    }
    return true
}

fun main(args: Array<String>) {
    println(isPalindrome("sugus"))
    println(isPalindrome("hello"))
    println(isPalindrome("gaga"))
    println(isPalindrome("x"))
    println(isPalindrome(""))
}

true
false
false
true
true

version récursive:

fun isPalindrome (s: String): Boolean {
    if (s.length <= 1) {
        return true
    }
    return (s.first() == s.last()) && isPalindrome(s.substring(1 until s.length-1))
}

supprimer les espaces et les caractères inconnus

fun String.sanitize(): String {
    return this.toLowerCase().filter{c -> c.isLetter()}
}

fun main(args: Array<String>) {
    println(isPalindrome2("elu par cette crapule"))
    println(isPalindrome2("elu par cette crapule".sanitize()))
}

false
true

Le plus long mot du dictionnaire français qui est un palindrome:

import java.io.File

const val wordlist = "data/french.txt"

fun String.sanitize(): String {
    return this.toLowerCase().filter{c -> c.isLetter()}
}

fun String.isPalindrome(): Boolean {
    if (this.length <= 1) {
        return true
    }
    return (this.first() == this.last()) && (this.substring(1 until this.length-1).isPalindrome())
}

fun main(args: Array<String>) { 
    var result: ArrayList<String> = ArrayList()
    var maxLen: Int = -1
    File(wordlist).forEachLine {
        x ->
        if (x.sanitize().isPalindrome()) {
            if (x.length > maxLen) {
                result = ArrayList()
                maxLen = x.length
            }
            if (x.length == maxLen) {
                result.add(x)
            }
        }
    }
    println(result)
}

[essayasse, ressasser]