51 lines
926 B
Go
51 lines
926 B
Go
package prime
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const testVersion = 2
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var sieve []int64
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var iter int
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func Factors(num int64) []int64 {
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if len(sieve) == 0 {
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sieve = append(sieve, int64(2))
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}
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switch num {
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case 1:
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return []int64{}
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case 2:
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return []int64{2}
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}
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for i := range sieve {
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if sieve[i] == num {
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// It's a prime already in the sieve
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return []int64{num}
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}
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if num%sieve[i] == 0 {
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div := (num / sieve[i])
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return append([]int64{sieve[i]}, Factors(div)...)
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}
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}
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// If we're here, we don't have the prime factors for this number
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topPrime := sieve[len(sieve)-1]
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for i := sieve[0]; i*topPrime <= num; i++ {
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// Check if i is a prime
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isPrime := true
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for j := range sieve {
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if i%sieve[j] == 0 {
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// Not a prime
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isPrime = false
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break
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}
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}
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if isPrime {
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// Found a new prime
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sieve = append(sieve, i)
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// New data, recurse
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return Factors(num)
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}
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}
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// Is this a prime?
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return []int64{num}
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}
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