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  1. package main
  2.  
  3. import (
  4. 	"fmt"
  5. )
  6.  
  7. type PrimeGenerator struct {
  8. 	primeChan chan uint32
  9. }
  10.  
  11. func NewPrimeGenerator() *PrimeGenerator {
  12. 	primeGenerator := PrimeGenerator{
  13. 		primeChan: make(chan uint32),
  14. 	}
  15.  
  16. 	go primeGenerator.start()
  17.  
  18. 	return &primeGenerator
  19. }
  20.  
  21. func (p *PrimeGenerator) start() {
  22. 	multiples := map[uint32]uint32{}
  23.  
  24. 	p.primeChan <- 2
  25. 	for num := uint32(3); ; num += 2 {
  26. 		factor, hasFactor := multiples[num]
  27. 		if hasFactor {
  28. 			delete(multiples, num)
  29. 		} else {
  30. 			factor = num << 1
  31. 		}
  32.  
  33. 		for newNum := num + factor; ; newNum += factor {
  34. 			_, hasNewFactor := multiples[newNum]
  35. 			if !hasNewFactor {
  36. 				multiples[newNum] = factor
  37. 				break
  38. 			}
  39. 		}
  40.  
  41. 		if !hasFactor {
  42. 			p.primeChan <- num
  43. 		}
  44. 	}
  45. }
  46.  
  47. func (p *PrimeGenerator) Next() uint32 {
  48. 	return <- p.primeChan
  49. }
  50.  
  51. func main() {
  52. 	n := 1000000
  53. 	primeGenerator := NewPrimeGenerator()
  54. 	for i := 1; i < n; i++ {
  55. 		primeGenerator.Next()
  56. 	}
  57. 	fmt.Printf("%d番目の素数: %d", n, primeGenerator.Next())
  58. }
Success #stdin #stdout 2.28s 49712KB
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1000000番目の素数: 15485863
https://ideone.com/DEfeV2
language:
Go (go 1.12.1)
created:
7 years ago
visibility:
public

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