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Daily Challenge #1 - String Peeler

thepracticaldev profile image dev.to staff ・1 min read

Hey, everyone. We've decided to host a daily challenge series. We'll have a variety of challenges, ranging in difficulty and complexity. If you choose to accept the task, your goal is to write the most efficient function you can for your language. Bonus points for any features you add!

I’ll start you off with a simple, straightforward challenge. Our first one comes from user @SteadyX on CodeWars.

Your goal is to create a function that removes the first and last letters of a string. Strings with two characters or less are considered invalid. You can choose to have your function return null or simply ignore.

The fundamentals are important, it only gets more difficult from here.

Happy coding!


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 (112)

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alvaromontoro profile image
Alvaro Montoro • Edited

CSS

Just add the class removeFirstAndLastLetter to a tag, and see the first and last letter "removed" from the text 😋

.removeFirstAndLastLetter {
  background: #fff;
  font-family: monospace;
  white-space: nowrap;
  position: relative;
  display: inline-block;
}

.removeFirstAndLastLetter::before,
.removeFirstAndLastLetter::after {
  content: "\00a0";
  background: #fff;
  top: 0;
  display: block;
  position: absolute;
  height: 100%;
  width: auto;
}

.removeFirstAndLastLetter::after {
  right: 0;
}
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And as an extra, it can be stylized and animated, so you can see the letters fade out:

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ben profile image
Ben Halpern

Ha! This one is great.

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alvaromontoro profile image
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taillogs profile image
Ryland G • Edited

JavaScript

(someString) => someString.length > 2 ? someString.slice(1, -1) : undefined;
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Python

someString[1:-1] if len(someString) > 2 else None
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C++

someString.size() > 2 ? someString.substr(1, someString.size() - 1) : null;
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C

int trimString(char someString[])
{
  if (strlen(someString) > 2) {
    char *copy = malloc((strlen(someString) - 2) * sizeof(char));
    memmove (copy, someString + 1, strlen(someString) - 2);
    printf("%s", copy);
    free(copy);
    return 0;
  }
  return 1;
}
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rafaacioly profile image
Rafael Acioly

Let people do something 😂

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jeromedeleon profile image
Jerome De Leon

HAHAHA damn. Let me finish my code LOL.

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powerc9000 profile image
Clay Murray • Edited

Let's just go wild

(someString) => {
   switch(someString.length){
   case 0:
   case 1:
   case 2:
       return null;
   default:
       const arr = someString.split("")
       arr.pop();
       arr.reverse();
       arr.pop();
       arr.reverse();
       return arr.join("")
   }
}

Why not?

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aybee5 profile image
Ibrahim Abdullahi Aliyu

This is indeed wild

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alvaromontoro profile image
Alvaro Montoro • Edited

In JavaScript it could be 24 bytes:

f=s=>s.slice(1,-1)||null
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andrewbrown profile image
Andrew Brown 🇨🇦 • Edited

I am surprised no one wrote test code. Sometimes in interviews with challenge this simple and you have access to run ruby they are expecting to see test code. Check out my ruby test code tutorials buds.

I notice lots of people are raising an error instead of ignoring or returning null so they have failed the challenge's instructions.

require "test/unit"

# remove the first and last letter of a string
# if there is less than 2 characters return zero.
def quartered value
  raise ArgumentError, 'Argument is not a string' unless value.is_a? String
  return value unless value.size > 2
  value[0] = ''
  value.chop
end


class QaurteredTest < Test::Unit::TestCase
  def test_quartered
    assert_equal 'orl', quartered('world'), "quartered('world') should return a string called 'orl'"
  end

  def test_quartered_ignore
    assert_equal 'hi', quartered('hi'), "quartered('hi') should return 'hi'"
  end

  def test_quartered_invalid
    assert_raise_message('Argument is not a string', "quartered(2) should raise exception") do
      quartered(2)
    end
  end
end
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ben profile image
Ben Halpern • Edited

Ruby


def remove_first_and_last(string)
  raise "Invalid" if string.size < 3
  string[1..string.size-2]
end
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databasesponge profile image
MetaDave 🇪🇺

I think you can get away with string[1..-2] there, Ben.

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v613 profile image
Ceban Dumitru • Edited

BASH

if [[ ${#1} > 2 ]]; then
    echo "${1:1:$(($#1-2))}";
else echo "not validated";
fi
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orenovadia profile image
orenovadia • Edited

I was surprised to find that -1 to work as well:

V=abcde
echo "${V:1:-1}"
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overlordex3 profile image
Exequiel Beker

I tried to not use any str function.

char* trimFirstAndLastLetters(char* str)
{
    int index = 1;

    if(str[0] == '\0' || str[1] == '\0') {
        return NULL;
    }

    while(*(str + index) != '\0') {
        *(str + (index - 1)) = *(str + index);
        index++;
    }

    /* Remove last one */
    *(str + (index - 2)) = '\0';
    return str;
}
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coreyja profile image
Corey Alexander • Edited

Rust

fn remove_first_and_last(string: &str) -> &str {
    remove_first_and_last_n_chars(&string, 1)
}

fn remove_first_and_last_n_chars(string: &str, chars_to_remove: usize) -> &str {
    if string.len() <= (2 * chars_to_remove) {
        panic!("Input string too short")
    }
    let start = chars_to_remove;
    let end = string.len() - 1 - chars_to_remove;

    &string[start..end]
} 

fn main() {
    println!("Ans: {}", remove_first_and_last("Hello, world!"));
    println!("Ans: {}", remove_first_and_last_n_chars("Hello, world!", 2));
    println!("Ans: {}", remove_first_and_last_n_chars("aa", 1));
    println!("Ans: {}", remove_first_and_last_n_chars("aa", 2));
}

View it in the Rust Playground here: play.rust-lang.org/?version=stable...

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barbaraips profile image
Bárbara Perdigão • Edited

I wanted to take my chances with these challenges, but I decided to start from the beginning, so here's my (super) late entry, done in Java :

public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("Type the word:");
        String word = scan.nextLine();

        if (word.length() > 2) {
            System.out.printf("Result: %s%n", word.substring(1, word.length() - 1));
        } else {
            System.out.println("Invalid word.");
        }

}
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andreasjakof profile image
Andreas Jakof

in C# as Extension-Method

public static string Peel(this string toPeel)
{
    int residual = toPeel.Length -2;
    if (residual < 1) return null;

    return toPeel.SubString(1,residual); //skip the first and take all but the last char
}
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vguleaev profile image
Vladislav Guleaev • Edited
function removeChar(str){
 return str.substr(1, str.length - 2)
};
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martyhimmel profile image
Martin Himmel

PHP

function remove_string_ends($str) {
    if (strlen($str) <= 2) {
        return null;
    }
    return substr($str, 1, -1);
}
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claudioscatoli profile image
Claudio Scatoli • Edited

I like that substr trick with the -1, didn't think of that!

How about this one liner?

<?php

function trimThis(string $str)
{
    return (mb_strlen($str) <= 2) ? null : substr($str,1,-1);
}


Use mb_string to support multibyte chars, such as Chinese

Also typehinted the argument, you never know...


This one is even shorter, possible only if the arg is typehinted tho

<?php
function trimThis(string $str) {
    return substr($str,1,-1) ?: null;
}

When the string is shorter than 2, substr returns false;
when the length is 2, substr returns "".

In both cases it's false, the the return is null.


Edit: many typos, I'm on mobile :/

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coreyja profile image
Corey Alexander • Edited

Ruby

Basic

def remove_first_and_last(some_string)
  raise 'Not long enough' unless some_string.length > 2

  some_string[1..-2]
end

Extra

def remove_first_and_last_n_characters(some_string, chars_to_remove: 1)
  raise 'Not long enough' unless some_string.length > (chars_to_remove * 2)

  start_index = chars_to_remove
  end_index = -1 - chars_to_remove
  some_string[start_index..end_index]
end
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rafi993 profile image
Rafi • Edited

solution in SQL (postgres)

\set str 'hello world'

select (
     case
       when (select length(:'str') > 2) 
        then (select substr(:'str', 2, length(:'str') - 2) ) 
else 'invalid string' end );
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johncip profile image
jmc

Clojure:

(defn trim [s]
  (apply str (drop-last (rest s))))
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lessp profile image
Tom Ekander

ReasonML

let strip = text =>
  String.(
    length(text) > 2
      ? switch (sub(text, 1, length(text) - 2)) {
        | s => Some(s)
        | exception _ => None
        }
      : None
  );

strip("hello"); // Some("ell")
strip("ab"); // None
strip(""); // None
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kaspermeyer profile image
Kasper Meyer • Edited

Ruby solution

require "minitest/autorun"

class WordTrimmer
  def initialize word
    @word = word
  end

  def trim
    @word.length <= 2 ? @word : @word[1..-2]
  end
end

class WordTrimmerTest < MiniTest::Test
  def test_removing_first_and_last_letter
    assert_equal "aspe", WordTrimmer.new("kasper").trim
  end

  def test_ignoring_two_letter_word
    assert_equal "hi", WordTrimmer.new("hi").trim
  end

  def test_ignoring_one_letter_word
    assert_equal "I", WordTrimmer.new("I").trim
  end
end
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praneetnadkar profile image
Praneet Nadkar • Edited

In C#, I would use in built string function Trim()
In my opinion we don't need Substring() here.
Just call :

readedInput.Trim(readedInput[0], readedInput[readedInput.Length - 1])

With 2 length validation:

var trimmed = readedInput.Length > 2 ? readedInput.Trim(readedInput[0], readedInput[readedInput.Length - 1]) : "Invalid" ;
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andreasjakof profile image
Andreas Jakof

But what if the input would be "aaajldflbbb"?

When using Trim(char[]), all appearances of the characters given to the method at the beginning and at the end, will be removed, leaving "jldfl".

Removes all leading and trailing occurrences of a set of characters specified in an array from the current String object.

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mwlang profile image
Michael Lang

Ruby Language Version

With specs

def trim value
  value.to_s[1...-1]
end

require "spec"

describe "#trim" do
  it { expect(trim "Foo Bar").to eq "oo Ba"}
  it { expect(trim "Foo").to eq "o"}
  it { expect(trim "Fo").to eq ""}
  it { expect(trim "F").to eq ""}
  it { expect(trim nil).to be_nil}
  it { expect(trim 777).to eq "7"}
end

output

>> rspec debook_ends.rb
......

Finished in 0.00696 seconds (files took 0.15187 seconds to load)
6 examples, 0 failures
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jasman7799 profile image
Jarod Smith

// "enterprise" solution
function peelString(str = '')
{
  //validate
  if(typeof(str) != 'string')
    throw new Error(`${str}, ${typeof(str)} is not a string`);
  if(str.length <= 2)
    throw new Error(`${str} does not have atleast 3 letters`);

  // process
  return str.substring(1,str.length-1);
}

My "enterprise" solution

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gypsydave5 profile image
David Wickes

Factor

USING: kernel math sequences ;
IN: dev.to-daily-challenge

: not-first-and-last ( str -- str ) dup length 2 >  [ rest but-last ] [ ] if ;

and some tests

USING: tools.test dev.to-daily-challenge ;
IN: dev.to-daily-challenge.tests

{ "ell" } [ "hello" not-first-and-last ] unit-test
{ "e" } [ "hel" not-first-and-last ] unit-test
{ "ha" } [ "ha" not-first-and-last ] unit-test
{ "" } [ "" not-first-and-last ] unit-test
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peterbunting profile image
Peter Bunting

In F#. Not the most straightforward way to solve this, but I wanted to use the language Array splicing.

let stringToByteArray (s:string)= System.Text.Encoding.ASCII.GetBytes s
let byteArraySplice x y (b: byte[]) = b.[x..y]
let byteArrayToString (b: byte[]) = System.Text.Encoding.ASCII.GetString b

let stringPeeler s = 
    s
    |> stringToByteArray
    |> byteArraySplice 1 (s.Length - 2)
    |> byteArrayToString

printfn "%s" <| stringPeeler "abcdefgh"
printfn "%s" <| stringPeeler "ab"
printfn "%s" <| stringPeeler "a"
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peterbunting profile image
Peter Bunting

And it turns out that you don't even need to explicitly convert it to an array. F# will let you do splicing on a string. So a much better solution is:

let stringPeeler (s: string) = s.[1..(s.Length - 2)]
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celyes profile image
Ilyes Chouia • Edited

PHP:


function removeFirstAndLastLetter($text){
    return substr($text, 1, -1);
}
echo removeFirstAndLastLetter("Oh no, I lost two letters");

// Outputs : h no, I lost two letter


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tblanshard profile image
Tallie

My solution using Python and list comprehension :)

def stringPeeler(string_to_peel):
    if len(string_to_peel) > 2:
        return "".join([x for i, x in enumerate(list(string_to_peel)) if (len(string_to_peel) - 1) > i > 0])
    else:
        return None
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pmkroeker profile image
Peter

Solution in Go:

package main

import (
    "fmt"
)

func main() {
    p, err := peel("hello")
    if err != nil {
        panic(err)
    }
    fmt.Println(p)
}

func peel(s string) (string, error) {
    if len(s) < 3 {
        return "", fmt.Errorf("Input string too short")
    }
    return s[1 : len(s)-1], nil
}

Running example in Go Playground

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kerldev profile image
Kyle Jones

In Python:

def peel_string(text):
    if len(text) > 2:
        return text[1:(len(text) - 1)]
    return None

print(peel_string("Testing"))
print(peel_string("Hi"))
print(peel_string(""))
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scrabill profile image
Shannon Crabill

I liked today's challenge so I'm going back to do past ones

def string_peeler(string)
  if string.length > 2
    string.delete(string[0]).delete(string[-1])
  end
end

Returns

string_peeler("hi") => nil 
string_peeler("killer") => "ille" 
string_peeler("BOB") => "O" 
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chukkyiii profile image
Jesse Godwin • Edited

Python

def string_peeler(string):
    stringarr = []
    newstring = ''

    for x in string:
        stringarr.append(x)

    del(stringarr[0])
    del(stringarr[-1])

    for em in stringarr:
        newstring += em
    print(newstring)

string_peeler('Missing two letters')

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rvictorino profile image
Robin Victorino • Edited

Hi!

A bit late to the party, but here's a Groovy one:

String peel(String toPeel) {
    if(!(toPeel?.length() > 2)) {
        throw new Exception('Can\'t peel a string shorter than 3 characters')
    }
    return toPeel[1..-2]
}
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flamangoes profile image
flamangoes

My approach in groovy...

Not sure if "ignore <2 chars" means "don't consider" or "ignore the trimming"

Don't consider =>

String peel(String toPeel) {
    toPeel[1..-2]
}

Ignore =>

String peel(String toPeel) {
    toPeel?.length() >2 ? toPeel[1..-2] : toPeel
}

I don't like returning null.