Range of a SWIFT Array

Question

I have an array of bytes and I need to find out in which track (startindex and endindex) a byte this or if only has startindex

ex:

var Faixa1:Array<UInt16> = [2,4,6,8,10,11,12]
var Faixa2:Array<UInt16> = [1,2]

var Valor1:UInt16 = 2
var Valor2:UInt16 = 3

//valor1 na faixa1
//startindex: 2
//endindex: 2

//valor1 na faixa2
//startindex: 2
//endindex: 2

//valor2 na faixa1
//startindex: 2
//endindex: 4