数组 – Swift 2计数重复数组

var test = [1,2,3,4,5,6,7,8,5,9,3,3,9,9,9]

var testCount = [Int:Int]()

for curr in test {
    if let x = testCount[curr] {
        testCount[curr] = x  + 1
        continue;
    }
    testCount[curr] = 1
}

print(testCount)

我正在努力,以便有类似的东西：

test.map_duplicate() or map_duplicate(test)

extension SequenceType where Self.Generator.Element: Hashable {
    func freq() -> [Self.Generator.Element: Int] {
        return reduce([:]) { (var accu: [Self.Generator.Element: Int], element) in
            accu[element] = accu[element]?.successor() ?? 1
            return accu
        }
    }
}