Day 0: Mean, Median, and Mode

10 Days of Statistics Day 0: Mean, Median, and Mode

/*
10 Days of Statistics
Objective 
In this challenge, we practice calculating the mean, median, and mode. Check out the Tutorial tab for learning materials and an instructional video!

Task 
Given an array, , of  integers, calculate and print the respective mean, median, and mode on separate lines. If your array contains more than one modal value, choose the numerically smallest one.

Note: Other than the modal value (which will always be an integer), your answers should be in decimal form, rounded to a scale of  decimal place (i.e., ,  format).

Input Format

The first line contains an integer, , denoting the number of elements in the array. 
The second line contains  space-separated integers describing the array's elements.

Constraints

, where  is the  element of the array.
Output Format

Print  lines of output in the following order:

Print the mean on a new line, to a scale of  decimal place (i.e., , ).
Print the median on a new line, to a scale of  decimal place (i.e., , ).
Print the mode on a new line; if more than one such value exists, print the numerically smallest one.
Sample Input

10
64630 11735 14216 99233 14470 4978 73429 38120 51135 67060
Sample Output

43900.6
44627.5
4978
Explanation

Mean: 
We sum all  elements in the array, divide the sum by , and print our result on a new line.

Median: 
To calculate the median, we need the elements of the array to be sorted in either non-increasing or non-decreasing order. The sorted array . We then average the two middle elements:

and print our result on a new line.
Mode: 
We can find the number of occurrences of all the elements in the array:

 4978 : 1
11735 : 1
14216 : 1
14470 : 1
38120 : 1
51135 : 1
64630 : 1
67060 : 1
73429 : 1
99233 : 1
Every number occurs once, making  the maximum number of occurrences for any number in . Because we have multiple values to choose from, we want to select the smallest one, , and print it on a new line.

*/


import Foundation

func mean(numbers: [Int]) -> Double {
    var sum = 0.0
    for number in numbers {
        sum += Double(number)
    }
    let mean = sum / Double(numbers.count)
    return mean
}

func median(numbers: [Int]) -> Double {
    let sortedNumbers = numbers.sorted(by: { num1, num2 in
        return num1 < num2 })
    
    let midIndex = numbers.count / 2
    var median = Double(sortedNumbers[midIndex])
    if(numbers.count % 2 == 0){
        median = Double(sortedNumbers[midIndex] + sortedNumbers[midIndex - 1]) / Double(2)
    }
    
    return median
}

func mode(numbers: [Int]) -> Int {
    let sortedNumbers = numbers.sorted(by: { num1, num2 in
        return num1 < num2 })
    
    var count = 0
    var current = sortedNumbers[0]
    var mode = 0
    var highOccurance = 0
 
    for var i in 0..<sortedNumbers.count{
        if(sortedNumbers[i] == current){
            count = count + 1
        }else{
            count = 1
            current = sortedNumbers[i]
        }
        if(count > highOccurance){
            highOccurance = count
            mode = sortedNumbers[i]
        }
    }
    //    var highestPair: (key: Int, value: Int) = (0, 0)
    //    for (key, value) in occurrences {
    //        highestPair = (value > highestPair.value) ? (key, value) : highestPair
    //    }
//        print(highestPair)
//        print(sortedNumbers)
//         print(occurrences)
    return mode
}
//let number = Int(readLine(strippingNewline: true)!)!
//let arrValue = readLine(strippingNewline: true)!.characters
//    .split {$0 == " "}
//    .map (Int.init)
//print(mean(numbers: arrValue))
//print(median(numbers: arrValue))
//print(mode(numbers: arrValue))
//let arrValue = [1,1,1,2,2,2,3,3]
//print(mode(numbers: arrValue))


let stdout = ProcessInfo.processInfo.environment["OUTPUT_PATH"]!
FileManager.default.createFile(atPath: stdout, contents: nil, attributes: nil)
let fileHandle = FileHandle(forWritingAtPath: stdout)!

guard let n = Int((readLine()?.trimmingCharacters(in: .whitespacesAndNewlines))!)
    else { fatalError("Bad input") }

guard let arTemp = readLine() else { fatalError("Bad input") }
let ar: [Int] = arTemp.split(separator: " ").map {
    if let arItem = Int($0.trimmingCharacters(in: .whitespacesAndNewlines)) {
        return arItem
    } else { fatalError("Bad input") }
}

guard ar.count == n else { fatalError("Bad input") }

let result = mean(numbers: ar)
let result2 = median(numbers: ar)
let result3 = mode(numbers: ar)

fileHandle.write(String(result).data(using: .utf8)!)
fileHandle.write("\n".data(using: .utf8)!)
fileHandle.write(String(result2).data(using: .utf8)!)
fileHandle.write("\n".data(using: .utf8)!)

fileHandle.write(String(result3).data(using: .utf8)!)
fileHandle.write("\n".data(using: .utf8)!)