LeetCode/kt/longest-nice-subarray.kt

class Solution {
    private data class Acc(var used: Int, var start: Int, val max: Int) {
        constructor() : this(0, 0, 0)

        fun update(
            nums: IntArray,
            end: IndexedValue<Int>,
        ): Acc {
            // shrink from left until conflict gets resolved
            while (used.and(end.value) != 0) {
                used = used.xor(nums[start])
                ++start
            }

            return copy(
                used = used.or(end.value),
                max = maxOf(max, end.index - start + 1),
            )
        }
    }

    fun longestNiceSubarray(nums: IntArray): Int =
        nums.withIndex().fold(Acc()) { acc, end ->
            acc.update(nums, end)
        }.max
}