findLongestSubstring.kt

package org.example

import kotlin.math.max

fun main() {
    val string = "abcaabgfhdbchfythgjgtuitijgjghjfhhdnnslphopoootkjjajhaabxvcgftyyihkjonpm"
    val result = findLongestSubstring(string)

    println("result: $result")
    println("asserted: ${(result == 9)}")
}

fun findLongestSubstring(string: String): Int {
    val chars: MutableSet<Char> = mutableSetOf()
    var left = 0
    var maxLength = 0
    for (right in string.withIndex()) {
        while (chars.contains(right.value)) {
            chars.remove(string[left])
            left++
        }
        chars.add(right.value)
        maxLength = max(maxLength, right.index - left + 1)
    }

    return maxLength
}