# Daily Challenge #9 - What's Your Number?

Write a function that accepts an array of 10 integers (between 0 and 9), that returns a string of those numbers in the form of a phone number.

The returned format must be correct in order to complete this challenge.
Don't forget the space after the closing parentheses!

Today's challenge comes from user xDranik on Codewars

Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

Want to propose a challenge for a future post? Email yo+challenge@dev.to with your suggestions!

### Discussion

I think this challenge description is very country specific, as every country has a different way of formatting these.

I agree with the other commentors that we need an example in the post to make it easier to understand! Especially with all the different ways telephone numbers are handled country to country.

Luckily the linked Codewars page has an example!

createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]) // => returns "(123) 456-7890"


JavaScript

I assumed the US phone number format that is (XXX) XXX-XXXX

const formatNumber = numbers => {

let phoneNumber = "";

// prerequisites:
//   - input must be an array
//   - with 10 elements
//   - each element will be a single digit number
if (
Array.isArray(numbers) &&
numbers.length === 10 &&
numbers.every(n => n > -1 && n < 10)
) {
// break the phone number into parts and generate the formmated string
const areaCode = numbers.slice(0,3).join('');
const firstPart = numbers.slice(3,6).join('');
const secondPart = numbers.slice(6).join('');
phoneNumber = (${areaCode})${firstPart}-${secondPart}; } return phoneNumber; }  Live demo on CodePen (with an alternative version in one line). Why the one line solution? No real reason. Both do the same, the first one is more verbose and easier to understand. I deleted the one-line one to avoid any confusion. Nim import strutils from sequtils import map const phone_number = @[1, 2, 3, 4, 5, 6, 7, 8, 9, 0] proc createPhoneNumber(numbers: seq[int]): string = if len(numbers) < 10: raise newException(ValueError, "invalid length provided to createPhoneNumber(), requires 10 digits") return "($#$#$#) $#$#$#-$#$#$#$#" % numbers.map(proc (p: int): string = intToStr(p)) # Run echo createPhoneNumber(phone_number)  Well I think I've found my new language I want to learn. Could you provide an example? The length and format tends to differ in different countries. In Costa Rice, for example, it might be 8 or 11 numbers long; as in 8765-4321, or, with the country code, (+506) 8765-4321. Either way it’s not 10 characters. Thanks! That's not the first time a challenge is not well explained. You need to grab the whole problem description here to let people give possible solutions. I like these challenges but need a good and clear description of the problem, why don't connect to codewars directly? #! /usr/bin/perl use warnings; use strict; sub phone_num { local$" = "";
"(@_[0 .. 2]) @_[3..5]-@_[6..9]"
}

use Test::More tests => 1;
is phone_num(0 .. 9), '(012) 345-6789';


The special variable $" is used to separate arrays interpolated in double quotes. By default, it contains a space, but we need the numbers to be adjacent, so we set it locally (i.e. in a dynamic scope) to an empty string. Another possible short solution is sub phone_num { "(012) 345-6789" =~ s/(\d)/$_[$1]/gr }  The substitution replaces each digit in the template string with the corresponding element of the @_ array which keeps the list of the subroutine arguments. /g means "global", it's needed to replace all the digits, not just the first one. The /r means "return" - normally, a substitution changes the bound left-hand side value, but with /r, it just returns the value. Nice, basically what I got. sprintf works as well. #!/usr/bin/env perl use strict; use warnings; sub createPhoneNumber { sprintf "(%s%s%s) %s%s%s-%s%s%s%s", @_; # local$" = "";
# "(@_[0..2]) @_[3..5]-@_[6..9]";
}

print createPhoneNumber(1, 2, 3, 4, 5, 6, 7, 8, 9, 0) . "\n";


The regex solution was pretty interesting. Thanks for the explanation!

python3

#!/usr/bin/env python3

def createPhoneNumber(array_of_integers):
return "(%s%s%s) %s%s%s-%s%s%s%s" % tuple(array_of_integers)

if __name__ == '__main__':
print(createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]))


Erlang: (in the REPL)

Num = [8,0,0,5,5,5,1,2,1,2].
io:format("(~B~B~B) ~B~B~B-~B~B~B~B~n", Num).
(800) 555-1212
ok


Or you can use io_lib:format and assign the result to a variable instead.

Checking for valid input is fairly trivial, but the Erlang convention is to assume that something this far into the system is okay, and correct for the error by dying and letting the supervisor deal with it.

Python

var = input("Enter 10 integers: ")
var = list(var)

if len(var) != 10:
print("Invalid Entry")
else:
print('(',var[0],var[1],var[2],') ',var[3],var[4],var[5],'-',var[6],var[7],var[8],var[9], sep='')


anyone's skin crawling?

Here is the simple solution with PHP:

function createPhoneNumber($numbersArray) {$format = "(%s%s%s) %s%s%s-%s%s%s%s";

return sprintf(
$format,$numbersArray[0], $numbersArray[1],$numbersArray[2], $numbersArray[3],$numbersArray[4], $numbersArray[5],$numbersArray[6], $numbersArray[7],$numbersArray[8], $numbersArray[9] ); }  package utils import ( "errors" "fmt" "strconv" ) func FormatPhoneNumber(phoneNumberArray []int) (string, error) { if len(phoneNumberArray) != 10 { return "", errors.New("Array length must be 10") } return fmt.Sprintf("(%s) %s-%s", intArrayToString(phoneNumberArray[:3]), intArrayToString(phoneNumberArray[3:6]), intArrayToString(phoneNumberArray[6:])), nil } func intArrayToString(intArray []int) string { number := "" for _, num := range intArray { number += strconv.Itoa(num) } return number }  I am not a big fan of code challenges in this format. For one people can see other answers. That can skew your thinking before even attempting the challenge. Secondly I think you should submit your own answers on codewars, and then link it here. Only people that has passed the challenge would be able to see it. @ben definitely need a spoiler tag. Haskell (US formatting): formatNumber :: [Int] -> Maybe String formatNumber xs | length xs /= 10 = Nothing | not$ and $(map (<10) xs) ++ (map (>=0) xs) = Nothing | otherwise = Just$ "(" ++ (showSlice 0 3 xs) ++ ") " ++ (showSlice 3 3 xs) ++ "-" ++ (showSlice 6 4 xs)
where showSlice from len = concat . map show . take len . drop from


const iterative = (input: number[], schema: string = "(###) ###-####") => {
let result = schema;
input.forEach(number => (result = result.replace("#", String(number))));

return result;
};

const recursive = (
input: number[],
schema: string = "(###) ###-####",
result: string = schema
): string => {
if (head === undefined) return result;

return recursive(rest, schema, result.replace("#", String(head)));
};

export const createPhoneNumber = {
iterative,
recursive
};


Better late than never ;p

Here's my attempt in PHP

function formPhoneNumber(array $integers): string { if(count($integers) != 10) {
throw new Exception('Please provide a valid array!');
}

$phone = "("; foreach($integers as $index =>$number){
if($number < 10 &&$number >= 0){
$phone .=$number;
if($index == 2){$phone .= ") ";
}elseif($index == 5){$phone .= "-";
}
}else{
throw new Exception("One of the numbers is invalid!");
}
}
return $phone; } echo formPhoneNumber([4, 5, 5, 4, 5, 1, 7, 8, 9, 0]);  My Rust Solution and test cases! I felt this one was a little easier than some of the previous days, but nothing wrong with that! #[derive(Debug, PartialEq)] pub enum Error { InvalidLength, NotSingleDigitInput, } pub fn format_phone_numer(numbers: &[u32]) -> Result<String, Error> { if numbers.len() != 10 { Err(Error::InvalidLength) } else if numbers.iter().any(|x| *x > 9) { Err(Error::NotSingleDigitInput) } else { Ok(format!( "({}{}{}) {}{}{}-{}{}{}{}", numbers[0], numbers[1], numbers[2], numbers[3], numbers[4], numbers[5], numbers[6], numbers[7], numbers[8], numbers[9], )) } } #[cfg(test)] mod tests { use crate::*; #[test] fn it_for_a_valid_phone_number() { assert_eq!( format_phone_numer(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]), Ok("(123) 456-7890".to_string()) ); assert_eq!( format_phone_numer(&[3, 2, 1, 5, 5, 5, 3, 1, 6, 3]), Ok("(321) 555-3163".to_string()) ); } #[test] fn it_errors_invalid_length_phone_number() { assert_eq!( format_phone_numer(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 5, 6, 3]), Err(Error::InvalidLength) ); assert_eq!( format_phone_numer(&[1, 2, 3, 4, 5, 6, 7,]), Err(Error::InvalidLength) ); } #[test] fn it_errors_for_non_single_digit_numbers() { assert_eq!( format_phone_numer(&[10, 2, 3, 4, 5, 6, 7, 8, 9, 0]), Err(Error::NotSingleDigitInput) ); } }  Go: import ( "fmt" "strconv" "strings" ) func CreatePhoneNumber(numbers [10]uint) string { strs := []string{} for _, n := range numbers { strs = append(strs, strconv.FormatUint(uint64(n), 10)) } a := strings.Join(strs[:3], "") b := strings.Join(strs[3:6], "") c := strings.Join(strs[6:], "") return fmt.Sprintf("(%s) %s-%s", a, b, c) }  No PHP solutions yet? Here I come! <?php function phoneFormat(array$numbers): string
{
if (10 !== count($numbers)) { throw new \RuntimeException("Wrong input"); } array_unshift($numbers, '(%d%d%d) %d%d%d-%d%d%d%d');

return call_user_func_array('sprintf', \$numbers);
}

assert('(123) 456-7890' === phoneFormat([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]), "Function not functioning :-/");


But please edit the OP to explain what format do you want, not everybody comes from USA!

Ruby solution

require "minitest/autorun"

class PhoneNumberFormatter
def initialize digits
@digits = digits
end

def format
"(#{area_code}) #{central_office_code}-#{line_number}"
end

private

def area_code
@digits[0..2].join
end

def central_office_code
@digits[3..5].join
end

def line_number
@digits[6..9].join
end
end

class PhoneNumberFormatterTest < MiniTest::Test
def test_formatted_phone_number
output = PhoneNumberFormatter.new([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]).format

assert_equal "(123) 456-7890", output
end
end



Clojure:

(defn format-number [digits]
(apply format "(%s%s%s) %s%s%s-%s%s%s%s" digits))


Ruby

def phone_number(nums)
puts "(#{nums[0..2].join("")}) #{nums[3..5].join("")}-#{nums[6..-1].join("")}"
end

puts phone_number([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]) #(123) 456-7890
`