MissingPermElem

MissingPermElem.kt

fun solution(a: IntArray): Int {
    // First edge case: missing is the first nr
    if (a.isEmpty()) return 1

    a.sort()

    for (i in a.indices) {
        // Index 0 must be 1, Index 1 must be 2, and so on.
        // Whenever that's not true, we found our missing nr
        if (a[i] != i + 1) return i + 1
    }

    // Second edge case: missing is the last nr
    return a.size + 1
}