Решение

class Solution {
    fun thirdMax(nums: IntArray): Int {
        var a = Long.MIN_VALUE
        var b = Long.MIN_VALUE
        var c = Long.MIN_VALUE
        for (v in nums) {
            val x = v.toLong()
            if (x == a || x == b || x == c) continue
            if (x > a) {
                c = b
                b = a
                a = x
            } else if (x > b) {
                c = b
                b = x
            } else if (x > c) {
                c = x
            }
        }
        return if (c == Long.MIN_VALUE) a.toInt() else c.toInt()
    }
}