LeetCode/kt/solving-questions-with-brainpower.kt

class Solution {
    private data class Question(val answered: Long, val skipped: Long) {
        companion object {
            private fun getWithOffset(
                stack: List<Question>,
                offset: Long,
            ): Long =
                (stack.size.toLong() - offset - 1).let { i ->
                    when {
                        i < 0 || i >= stack.size.toLong() -> 0
                        else -> stack[i.toInt()].max
                    }
                }
        }

        val max: Long
            get() = maxOf(answered, skipped)

        constructor(q: IntArray, stack: List<Question>) : this(
            answered = q[0].toLong() + getWithOffset(stack, q[1].toLong()),
            skipped = getWithOffset(stack, 0),
        ) {}
    }

    fun mostPoints(questions: Array<IntArray>): Long =
        mutableListOf<Question>().let { st ->
            questions.asIterable().reversed().forEach { q ->
                st.add(Question(q, st))
            }

            st.last().max
        }
}