Set add instead of contains

SetInsteadContains.kt

fun <T> List<T>.hasDuplicates(): Boolean {
    val accumulator = mutableSetOf<T>()
    return any { !accumulator.add(it) }
}

fun main() {
    println(listOf(1, 2, 5).hasDuplicates())
    println(listOf(-5, 8, 0, 8).hasDuplicates())
    println(emptyList<Int>().hasDuplicates())
}