package leetcode_study

import io.kotest.matchers.shouldBe

import org.junit.jupiter.api.Test

class `missing-number` {

fun missingNumber(nums: IntArray): Int {

return usingSum(nums)

}

/**

private fun usingIndex(nums: IntArray): Int {

val existed = BooleanArray(nums.size + 1)

nums.forEach { existed[it] = true }

existed.forEachIndexed { i, e ->

if (!e) return i

}

return -1

}

/**

private fun usingSum(nums: IntArray): Int {

val size = nums.size

return nums.fold((size + 1) * size / 2) { acc , i -> acc - i }

}

@Test

fun `입력받은 정수 배열에서 비어있는 정수를 반환한다`() {

missingNumber(intArrayOf(3,2,1)) shouldBe 0

missingNumber(intArrayOf(3,0,1)) shouldBe 2

missingNumber(intArrayOf(9,6,4,2,3,5,7,0,1)) shouldBe 8

}

}