A mono-alphabetic cipher is a simple substitution cipher where each letter of the sentence is replaced with another letter of the alphabet. It uses a fixed key which consists of the 26 letters of a shuffled alphabet.

Hello @nikhilkala , can one make PRs to improve already existing solutions? An example is the factorial solution which will be faster for large numbers if a cache is implemented

This PR add solution for project euler problem 1 and problem 2.

Apart from this PR, i have questions and sugesstions for this repo:

1. why not add psr-4 autoloading to composer.json file, something like:

{
    "autoload": {
        "psr-4": {
            "TheAlgorithms\\PHP\\": "app/",
        }
    },
    "autoload-dev": {
        "psr-4": {
            "TheAlgorithms\\PHP\\Tests\\": "tests/"
        }
    },
}

imo, it would help manage namespaces and classes.

current implementation: if i want to use factorial function from Maths\Factorial.php, i must require the file with:

require_once 'path/to/Factorial.php';

$x = factorial(100);

but if we use namespace, we can do:

// file: Math\Factorial.php
namespace TheAlgorithms\PHP\Maths;

function factorial($number) {
//....
}

// file: Anywhere.php
use function \TheAlgorithms\PHP\Maths\factorial;

$x = factorial(100);

or with classes and static function:

// file: Math.php
namespace TheAlgorithms\PHP;

class Math {
    public static function factorial($number) {
    //....
    }
}


// file: Anywhere.php
use \TheAlgorithms\PHP\Math;

$x = Math::Factorial(100);

2. i think it is better to use internal link in the DIRECTORY.md file instead of external link directly to github.

// current
## Maths
  * [Absolutemax](https://github.com/TheAlgorithms/PHP/blob/master/Maths/AbsoluteMax.php)

// propose:
## Maths
  * [Absolutemax](./Maths/AbsoluteMax.php)

with that, we can browse the file locally from our clonned repo.

3. what is the standard used here? i see the folder structure is kinda messy. there are lowercase folder, uppercase folder, camelcase fiename, etc. the tests folder is kinda messy too.

4. is there limit on maximal run time per function on tests? i see the project euler problem 5 taking soo much time to complete the test. would it be nice to add some rule? or do the test in parallel? also, what if changing the test with https://pestphp.com? it has simple syntax and more great expectation api to simplify the tests.

what do you think? i am happy to open a draft PR if any sugesstion is being considered.

#cmiiw #cheers :beers:

I'll be adding many more. Adjacency matrix/list, BFS, DFS, Cycle Detection, spanning tree's, Shortest Path, etc all in PHP. This commit is just to get started 🙂

Quick sort is very fast! Uses array shift to create separate arrays (less than or greater than the current value) and merges them together when there are none left.

This PR updates directory link from external to internal. This will make sure the links still works for local repository.

I also update the BASE_URL for the github action.

closes #38

Bug

isPrime() returns true to the square of a number, for example. isPrime(49) // return true instead of false

fix

-while ($i < sqrt($number)) {...}
+while ($i <= sqrt($number)) {...}

I have tried to adhere by Contributing Guidelines still if I missed something or made some error let me know and any further suggestions would be appreciated. Thanks.

I added few functions and a class to use NLP algorithms for string manipulation.

Please review and let me know your ideas. Hope you will love my contribution and I will contribute more on using PHP NLP Tools.

Create a geometry folder. Add area + cirumference function for a square. A simple test for the both function with some test values in geometryTest.php

Hi, the first clause of quickSort algorithm intended for checking empty inputs is using "isset" function which only checks for variable existence or null. So, if I call quickSort with an empty array ([ ]) this this clause will not work.

Also, using isset inside this function has not sense because the $input parameter is always defined and it will be always an array (nulls are not allowed with this arguments definition), so it will always evaluate to true.

I think it would be appropriate to use the "empty" function in this case instead.