flatten.swift

///input -  ["a": ["b": ["c": "1", "d": "1"]],
             "e" : "1" ,
              "f" : ["g": ["h": "1"]]]
///output - ["h": "1", "d": "1", "g": 1, "a": 3, "e": "1", "c": "1", "f": 2, "b": 2]

func flatten(dictionary: [String: Any]) -> [String: Any] {
    func flattenRec(output: inout [String: Any], keyPath: String, value: Any, count: inout Int) {
        let nCount =  count
        if value is String {
            output[keyPath] = value
        }
        if let dict = value as? [String: Any] {
            dict.forEach { key, value in
                count = count + 1
                flattenRec(output: &output, keyPath: key, value: value, count: &count)
            }
            output[keyPath] =  count - nCount
        }
    }

  var outputDict = [String: Any]()

  dictionary1.forEach { key, value in
    var count = 0
    flattenRec(output: &outputDict, keyPath: key, value: value, count: &count)
  }

  return outputDict
}
//{ "a": { "b": { "c": 1, "d": 1 }, "e": 1, "f": { "g": { "h" : 1}}} }
let dictionary1 = ["a": ["b": ["c": "1", "d": "1"]],
                   "e" : "1" ,
                   "f" : ["g": ["h": "1"]]] as [String : Any]
let output = flatten(dictionary: dictionary1)
print(output)
//"["h": "1", "d": "1", "g": 1, "a": 3, "e": "1", "c": "1", "f": 2, "b": 2]