# [Golang] Get All Prime Factors of Integer Number

*Prime Factorization* - Find all prime factors of a given integer number
in Go programming language.

The prime factorization algorithm comes from GeeksforGeeks [1]. Please go there for details of the algorithm and explanation.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | package pfs // Get all prime factors of a given number n func PrimeFactors(n int) (pfs []int) { // Get the number of 2s that divide n for n%2 == 0 { pfs = append(pfs, 2) n = n / 2 } // n must be odd at this point. so we can skip one element // (note i = i + 2) for i := 3; i*i <= n; i = i + 2 { // while i divides n, append i and divide n for n%i == 0 { pfs = append(pfs, i) n = n / i } } // This condition is to handle the case when n is a prime number // greater than 2 if n > 2 { pfs = append(pfs, n) } return } |

Testing:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | package pfs import ( "fmt" "testing" ) func TestPrimeFactors(t *testing.T) { if fmt.Sprintf("%v", PrimeFactors(23)) != `[23]` { t.Error(23) } if fmt.Sprintf("%v", PrimeFactors(12)) != `[2 2 3]` { t.Error(12) } if fmt.Sprintf("%v", PrimeFactors(360)) != `[2 2 2 3 3 5]` { t.Error(360) } if fmt.Sprintf("%v", PrimeFactors(97)) != `[97]` { t.Error(97) } } |

Tested on:

`Ubuntu Linux 17.04`,`Go 1.8.1`- Go Playground

References:

[1] | Efficient program to print all prime factors of a given number |

[2] | go - Checking the equality of two slices - Stack Overflow |