Kotlin -如何实现铁路围栏密码？

fun encryptRailFence(plainText: String, rails: Int): String {
    val fence = Array(rails) { CharArray(plainText.length) { ' ' } }
    var rail = 0
    var direction = 1

    for (i in plainText.indices) {
        fence[rail][i] = plainText[i]
        rail += direction

        if (rail == rails - 1 || rail == 0) {
            direction = -direction
        }
    }

    var encryptedText = ""
    for (i in 0 until rails) {
        for (j in plainText.indices) {
            if (fence[i][j] != ' ') {
                encryptedText += fence[i][j]
            }
        }
    }

    return encryptedText
}

fun decryptRailFence(encryptedText: String, rails: Int): String {
    val fence = Array(rails) { CharArray(encryptedText.length) { ' ' } }
    var rail = 0
    var direction = 1

    for (i in encryptedText.indices) {
        fence[rail][i] = '*'
        rail += direction

        if (rail == rails - 1 || rail == 0) {
            direction = -direction
        }
    }

    var index = 0
    for (i in 0 until rails) {
        for (j in 0 until encryptedText.length) {
            if (fence[i][j] == '*' && index < encryptedText.length) {
                fence[i][j] = encryptedText[index++]
            }
        }
    }

    var decryptedText = ""
    rail = 0
    direction = 1

    for (i in encryptedText.indices) {
        decryptedText += fence[rail][i]
        rail += direction

        if (rail == rails - 1 || rail == 0) {
            direction = -direction
        }
    }

    return decryptedText
}

fun main() {
    val plainText = "Hello, World!"
    val rails = 3

    val encryptedText = encryptRailFence(plainText, rails)
    println("Encrypted Text: $encryptedText")

    val decryptedText = decryptRailFence(encryptedText, rails)
    println("Decrypted Text: $decryptedText")
}