Could you please help me to simplify the flow below? the scope is to count how many time each element is duplicate within the given array.
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)
I'm working on it in order to have something like:
test.map_duplicate() or map_duplicate(test)
extension Array where Element: Hashable {
func mergeDuplicates() -> [Element: Int] {
var result = [Element: Int]()
self.forEach({ result[$0] = result[$0] ?? 0 + 1 })
return result
}
}
var test = [1,2,3,4,5,6,7,8,5,9,3,3,9,9,9]
let testCount = test.mergeDuplicates()
print(testCount)
The code above provides an extension to any Array type that holds Hashable elements (anything else is not eligible to be the key of a dictionary). Method mergeDuplicates produces the dictionary you want. In its implementation, forEach() executes a closure over every element in the array (this is typically more straightforward and transparent alternative to old-fashioned for-loop). Then on each iteration we check whether there is already existing value in the dictionary with a running count (and use nil-coalescing operator ?? to handle cases when a particular value was not yet met before, hence it's zero). Then increment, and store (back) into the dictionary.
You could extend SequenceType to have a function freq which does exactly what you need here.
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
}
}
}
var countForNumber = 0
for number in test {
test.forEach({ if number == $0 { countForNumber++ } })
testCount[number] = countForNumber
countForNumber = 0
}
