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Commitc5b12db

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SpiderMathactions-userappgurueu
authored
feat: Added Double Factorial Iterative Implementation (#187)
* Update DIRECTORY.md* 🚀feat: added double factorial (iterative)* Update DIRECTORY.md* removed redundant if check, fix formatting* Update DIRECTORY.md---------Co-authored-by: autoprettier <actions@github.com>Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
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‎DIRECTORY.md‎

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*[Calculate Median](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/calculate_median.ts)
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*[Degrees To Radians](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/degrees_to_radians.ts)
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*[Digit Sum](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/digit_sum.ts)
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*[Double Factorial Iterative](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/double_factorial_iterative.ts)
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*[Euler Totient](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/euler_totient.ts)
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*[Factorial](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/factorial.ts)
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*[Factors](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/factors.ts)
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*[Number Of Digits](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/number_of_digits.ts)
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*[Pascals Triangle](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/pascals_triangle.ts)
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*[Perfect Cube](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/perfect_cube.ts)
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*[Perfect Number](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/perfect_number.ts)
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*[Perfect Square](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/perfect_square.ts)
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*[Prime Factorization](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/prime_factorization.ts)
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*[Primes](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/primes.ts)
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/**
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*@function DoubleFactorialIterative
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*@description Calculate the double factorial of a number (iterative implementation)
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*@summary In mathematics, double factorial of a number n is denoted by n!!.
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* It is not to be confused with (n!)!, which is the factorial function iterated twice.
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* The double factorial is the product of all positive integers upto n that have the same parity (odd or even)
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* as n.
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* Therefore,
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* 9!! = 9 . 7 . 5 . 3 . 1
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* 10!! = 10 . 8 . 6 . 4 . 2
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*
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* Please note that for factorials of even numbers, the series ends at 2.
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*@see [Wikipedia](https://en.wikipedia.org/wiki/Double_factorial)
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*@see [Mathworld](https://mathworld.wolfram.com/DoubleFactorial.html)
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*@see [GeeksForGeeks](https://www.geeksforgeeks.org/double-factorial/)
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*@example DoubleFactorialIterative(4) = 8
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*@example DoubleFactorialIterative(5) = 15
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*/
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constDoubleFactorialIterative=(n:number)=>{
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if(n<0)thrownewRangeError("The number needs to be non-negative")
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letdoubleFactorial=1
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for(leti=n;i>0;i-=2)
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doubleFactorial*=i
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returndoubleFactorial
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}
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export{DoubleFactorialIterative}
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import{DoubleFactorialIterative}from"../double_factorial_iterative";
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describe("Double Factorial",()=>{
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test.each([[4,8],[5,15],[10,3840]])("%i!! = %i",(n,expected)=>{
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expect(DoubleFactorialIterative(n)).toBe(expected)
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})
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})

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