TheAlgorithms_Go/math/binomialcoefficient.go at master · cureking/TheAlgorithms_Go · GitHub

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// binomialcoefficient.go

// description: Returns C(n, k)

// details:

// a binomial coefficient C(n,k) gives number ways

// in which k objects can be chosen from n objects.

// wikipedia: https://en.wikipedia.org/wiki/Binomial_coefficient

// author: Akshay Dubey (https://github.com/itsAkshayDubey)

// see binomialcoefficient_test.go

package math

import (

"errors"

)

var ErrPosArgsOnly error = errors.New("arguments must be positive")

// C is Binomial Coefficient function

// This function returns C(n, k) for given n and k

func Combinations(n int, k int) (int, error) {

if n < 0 || k < 0 {

return -1, ErrPosArgsOnly

}

if k > (n - k) {

k = n - k

}

res := 1

for i := 0; i < k; i++ {

res *= (n - i)

res /= (i + 1)

}

return res, nil

}