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Implementing Permutations and Combinations #481

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Merged
itsvinayak merged 8 commits into from Nov 7, 2020
Merged

Implementing Permutations and Combinations #481

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e2a92fd
calculates the number of permutations and combinations
Oct 16, 2020
4a38307
calculates the number of permutations and combinations
Oct 16, 2020
6f5a026
calculates the number of permutations and combinations
Oct 16, 2020
944e41b
updating DIRECTORY.md
Oct 16, 2020
64a2c5b
calculates the number of permutations and combinations
Oct 16, 2020
8d3cff9
Merge branch 'master' of https://www.github.com/Shreyas-OwO/Javascript
Oct 16, 2020
15014ff
calculates the number of permutations and combinations
Oct 16, 2020
f87fc81
fixed a typo
Oct 16, 2020
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1 change: 1 addition & 0 deletions DIRECTORY.md
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* [PerfectCube](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PerfectCube.js)
* [PerfectNumber](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PerfectNumber.js)
* [PerfectSquare](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PerfectSquare.js)
* [PermutationAndCombination](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PermutationAndCombination.js)
* [PiApproximationMonteCarlo](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PiApproximationMonteCarlo.js)
* [Polynomial](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/Polynomial.js)
* [PrimeCheck](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/PrimeCheck.js)
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67 changes: 67 additions & 0 deletions Maths/PermutationAndCombination.js
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/**
* @details Calculates the number of permutations and combinations.
* @external_link (Permutation And Combinations)[https://www.geeksforgeeks.org/permutation-and-combination/]
*/

/**
* @brief Calculates the factorial of the given number.
* @param num: integer
* @details Factorial of n = n * (n - 1) * (n - 2) * ... * 1
* @returns integer: Factorial of the number.
NaN: if negative number is provided.
*/
const factorial = (n) => {
if (n >= 0) {
if (n === 0) {
return 1
} else {
return n * factorial(n - 1)
}
} else {
return NaN
}
}

/**
* @brief Calculates the number of Permutations from the given data.
* @param
* n: integer -> number of items.
* r: integer -> number of times n is taken.
* @returns integer: The number of permutations.
NaN: if negative number is provided.
*/
const permutation = (n, r) => {
return factorial(n) / factorial(n - r)
}

/**
* @brief Calculates the number of Combinations from the given data.
* @param
* n -> number of items.
* r -> number of times n is taken.
* @returns integer: The number of combinations.
NaN: if negative number is provided.
*/
const combination = (n, r) => {
return factorial(n) / (factorial(r) * factorial(n - r))
}

// Exports the functions to be used in other files.
module.exports.factorial = factorial
module.exports.permutation = permutation
module.exports.combination = combination

/**
* @example

const funcs = require("./PermutationAndCombination.js");

console.log(funcs.factorial(5));
console.log(funcs.permutation(5, 2));
console.log(funcs.combination(5, 2));

* @output
120
20
10
*/
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