Daily Challenge #9 - What's Your Number?

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Daily Challenge (114 Part Series)

1) Daily Challenge #1 - String Peeler 2) Daily Challenge #2 - String Diamond 3 ... 112 3) Daily Challenge #3 - Vowel Counter 4) Daily Challenge #4 - Checkbook Balancing 5) Daily Challenge #5 - Ten Minute Walk 6) Daily Challenge #6 - Grandma and her friends 7) Daily Challenge #7 - Factorial Decomposition 8) Daily Challenge #8 - Scrabble Word Calculator 9) Daily Challenge #9 - What's Your Number? 10) Daily Challenge #10 - Calculator 11) Daily Challenge #11 - Cubic Numbers 12) Daily Challenge #12 - Next Larger Number 13) Daily Challenge #13 - Twice Linear 14) Daily Challenge #14 - Square into Squares 15) Daily Challenge #15 - Stop gninnipS My sdroW! 16) Daily Challenge #16 - Number of People on the Bus 17) Daily Challenge #17 - Double Trouble 18) Daily Challenge #18 - Triple Trouble 19) Daily Challenge #19 - Turn numbers into words 20) Daily Challenge Post #20 - Number Check 21) Daily Challenge #21 - Human Readable Time 22) Daily Challenge #22 - Simple Pig Latin 23) Daily Challenge #23 - Morse Code Decoder 24) Daily Challenge #24 - Shortest Step 25) Daily Challenge #25 - Double Cola 26) Daily Challenge #26 - Ranking Position 27) Daily Challenge #27 - Unlucky Days 28) Daily Challenge #28 - Kill the Monster! 29) Daily Challenge #29 - Xs and Os 30) Daily Challenge #30 - What is the price? 31) Daily Challenge #31 - Count IPv4 Addresses 32) Daily Challenge #32 - Hide Phone Numbers 33) Daily Challenge #33 - Did you mean...? 34) Daily Challenge #34 - WeIrD StRiNg CaSe 35) Daily Challenge #35 - Find the Outlier 36) Daily Challenge #36 - Let's go for a run! 37) Daily Challenge #37 - Name Swap 38) Daily Challenge #38 - Middle Name 39) Daily Challenge #39 - Virus 40) Daily Challenge #40 - Counting Sheep 41) Daily Challenge #41 - Greed is Good 42) Daily Challenge #42 - Caesar Cipher 43) Daily Challenge #43 - Boardgame Fight Resolver 44) Daily Challenge #44 - Mexican Wave 45) Daily Challenge #45 - Change Machine 46) Daily Challenge #46 - ??? 47) Daily Challenge #47 - Alphabets 48) Daily Challenge #48 - Facebook Likes 49) Daily Challenge #49 - Dollars and Cents 50) Daily Challenge #50 - Number Neighbor 51) Daily Challenge #51 - Valid Curly Braces 52) Daily Challenge #52 - Building a Pyramid 53) Daily Challenge #53 - Faro Shuffle 54) Daily Challenge #54 - What century is it? 55) Daily Challenge #55 - Building a Pile of Cubes 56) Daily Challenge #56 - Coffee Shop 57) Daily Challenge #57 - BMI Calculator 58) Daily Challenge #58 - Smelting Iron Ingots 59) Daily Challenge #59 - Snail Sort 60) Daily Challenge #60 - Find the Missing Letter 61) Daily Challenge #61 - Evolution Rate 62) Daily Challenge #62 - Josephus Survivor 63) Daily Challenge #63- Two Sum 64) Daily Challenge #64- Drying Potatoes 65) Daily Challenge #65- A Disguised Sequence 66) Daily Challenge #66- Friend List 67) Daily Challenge #67- Phone Directory 68) Daily Challenge #68 - Grade Book 69) Daily Challenge #69 - Going to the Cinema 70) Daily Challenge #70 - Pole Vault Competition Results 71) Daily Challenge #71 - See you next Happy Year 72) Daily Challenge #72 - Matrix Shift 73) Daily Challenge #73 - ATM Heist 74) Daily Challenge #74 - Free Pizza 75) Daily Challenge #75 - Set Alarm 76) Daily Challenge #76 - Bingo! (or not...) 77) Daily Challenge #77 - Bird Mountain 78) Daily Challenge #78 - Number of Proper Fractions with Denominator d 79) Daily Challenge #79 - Connect Four 80) Daily Challenge #80 - Longest Vowel Change 81) Daily Challenge #81 - Even or Odd 82) Daily Challenge #82 - English Beggars 83) Daily Challenge #83 - Deodorant Evaporator 84) Daily Challenge #84 - Third Angle of a Triangle 85) Daily Challenge #85 - Unwanted Dollars 86) Daily Challenge #86 - Wouldn't, not Would. 87) Daily Challenge #87 - Pony Express 88) Daily Challenge #88 - Recursive Ninjas 89) Daily Challenge #89 - Extract domain name from URL 90) Daily Challenge #90 - One Step at a Time 91) Daily Challenge #91 - Bananas 92) Daily Challenge #92 - Boggle Board 93) Daily Challenge #93 - Range Extraction 94) Daily Challenge #94 - Last Digit 95) Daily Challenge #95 - CamelCase Method 96) Daily Challenge #96 - Easter Egg Crush Test 97) Daily Challenge #97 - Greed is Good 98) Daily Challenge #98 - Make a Spiral 99) Daily Challenge #99 - Balance the Scales 100) Daily Challenge #100 - Round Up 101) Daily Challenge #101 - Parentheses Generator 102) Daily Challenge #102 - Pentabonacci 103) Daily Challenge #103 - Simple Symbols 104) Daily Challenge #104 - Matrixify 105) Daily Challenge #105 - High-Sum Matrix Drop 106) Daily Challenge #106 - Average Fuel Consumption 107) Daily Challenge #107 - Escape the Mines 108) Daily Challenge #108 - Find the Counterfeit Coin 109) Daily Challenge #109 - Decorate with Wallpaper 110) Daily Challenge #110 - Love VS. Friendship 111) Daily Challenge #111 - 99 Bottles of Beer 112) Daily Challenge #112 - Functions of Integers on the Cartesian Plane 113) Daily Challenge #113 - Iterative Rotation Cipher 114) Daily Challenge #114 - Speed Control

Can I have 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!

twitter logo DISCUSS (20)
markdown guide
 

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).

 
 

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!

 

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.

 

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]))
 
#! /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!

 

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?

 

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!

EDIT: added length validation

 

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.

 

codesandbox.io/embed/daily-challen...

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 => {
  const [head, ...rest] = input;
  if (head === undefined) return result;

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

export const createPhoneNumber = {
  iterative,
  recursive
};
 

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
 

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

 

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)
        );
    }
}

 

Clojure:

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