Generate Sorted Dictionary by Letters from an Array Swift

Question

I have an Array of Departments' Names

var departments: Array<String>!

I want to sort this array alphabetically in Dictionary eg the dictionary should be like this

var MyDictionary = ["A": ["Affenpoo", "Affenpug", "Affenshire", "Affenwich", "Afghan Collie", "Afghan Hound"], "B": ["Bagle Hound", "Boxer"],
    "C": ["Cagle Cound", "Coxer"]]

the departments array is not static

how can i generate this dictionary in swift?

Thanks a lot

Answer 1

My approach would be to iterate the array and take the first letter of each entry. Retrieve the array from the dictionary for that letter. If it is nil create a new array. Add the word to the array you retrieved and then store the array in the dictionary.

let departments = ["Affenpoo", "Affenpug", "Affenshire", "Affenwich", "Afghan Collie","Cagle Cound", "Coxer"]
var outputDict=[String:[String]]()

for word in departments {
    let initialLetter=word.substringToIndex(word.startIndex.advancedBy(1)).uppercaseString
    var letterArray=outputDict[initialLetter] ?? [String]()
    letterArray.append(word)
    outputDict[initialLetter]=letterArray
}

print(outputDict)

["C": ["Cagle Cound", "Coxer"], "A": ["Affenpoo", "Affenpug", "Affenshire", "Affenwich", "Afghan Collie"]]

Answer 2

EDIT: solution by Paulw11 is more efficient

I don't think this question is relevant to swift in particular, but anyways try this:

let a = ["All", "Cat", "red", "gat", "Star sun", "bet you", "Zeta Fog", "Tea", "Fox"]

let b = a.map{ $0.lowercaseString }

let c = b.sort()
let d = c.map{ $0[$0.startIndex.advancedBy(0)]}

var dictionary:[String:[String]] = [:]
let byInitial = d.map{ initial in

    let clustered = c.filter{$0.hasPrefix("\(initial)")}
    dictionary.updateValue(clustered, forKey:"\(initial)")
}
print("\(dictionary)")