Binomial coefficient

nCr.go

package main

import "fmt"

func main() {
	//nCr
	n := 7
	r := 2
	c := BinCoeff(n, r)
	
	fmt.Println(c)
}

 
// BinCoeff (in combinatorics) gives the number of ways, disregarding order, 
// that k objects can be chosen from among n objects; more formally, the number of 
// k-element subsets (or k-combinations) of an n-element set
// ref: http://www.mathwords.com/c/combination_formula.htm
func BinCoeff(n int, k int) int64 {
	if k == 0 || k == n {
		return 1
	} else {
		return BinCoeff(n-1, k-1) + BinCoeff(n-1, k)
	}
}