StringTree Kotlin

stringtree.kt

import java.lang.IndexOutOfBoundsException

abstract class Node {
    var length: Int = 0

    abstract fun charAt(index: Int): Char
    abstract fun subString(start: Int, end: Int): String
    abstract fun delete(index: Int)
}

class InternalNode(length: Int = 0, var left: Node? = null, var right: Node? = null) : Node() {
    init {
        this.length = length
    }

    override fun charAt(index: Int): Char {
        if (index >= length) {
            throw IndexOutOfBoundsException()
        }
        if (left != null && index < left!!.length) {
            return left!!.charAt(index)
        }
        if (right != null) {
            return right!!.charAt(index - left!!.length)
        }
        throw IndexOutOfBoundsException()
    }

    override fun subString(start: Int, end: Int): String {
        val substr = StringBuilder()
        if (left != null && start < left!!.length) {
            substr.append(left!!.subString(start, minOf(end, left!!.length - 1)))
        }
        if (right != null && end >= left!!.length) {
            substr.append(right!!.subString(0, end - left!!.length))
        }
        return substr.toString()
    }

    override fun delete(index: Int) {
        if (index >= length) {
            throw IndexOutOfBoundsException()
        }
        if (left != null && index < left!!.length) {
            left!!.delete(index)
        }
        if (right != null) {
            right!!.delete(index - left!!.length)
        }
    }
}

class Leaf(var string: String = "", length: Int = 0) : Node() {
    init {
        if (length == 0) {
            this.length = string.length
        } else {
            this.length = length
        }
    }

    override fun charAt(index: Int): Char {
        if (index >= length) {
            throw IndexOutOfBoundsException()
        }
        return string[index]
    }

    override fun subString(start: Int, end: Int): String {
        return string.substring(start, end + 1)
    }

    override fun delete(index: Int) {
        if (index >= length) {
            throw IndexOutOfBoundsException()
        }
        string = string.substring(0, index) + string.substring(index + 1)
        length--
    }
}

class StringTree {
    var root: InternalNode = InternalNode()
}

fun main() {
    val leaf1 = Leaf(string = "ABCDE")
    val leaf2 = Leaf(string = "FGHIJKLMNO")
    val leaf3 = Leaf(string = "PQRSTUVWXYZ")
    val inode1 = InternalNode(21, left = leaf2, right = leaf3)
    val root = InternalNode(26, left = leaf1, right = inode1)

    println(root.charAt(25))
    println(root.subString(1, 3))
}