setIntersection.swift

func setIntersection(arr1: [Int], arr2: [Int]) -> [Int] {
    var result: [Int] = []
    var pointer1 = 0
    var pointer2 = 0
    
    while pointer1 < arr1.count && pointer2 < arr2.count {
        if arr1[pointer1] == arr2[pointer2] {
            result.append(arr1[pointer1])
            pointer1 = pointer1 + 1
            pointer2 = pointer2 + 1
        } else if arr1[pointer1] < arr2[pointer2] {
            pointer1 = pointer1 + 1
        } else {
            pointer2 = pointer2 + 1
        }
    }
    return result
}