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Erdős-primes (view source)

Revision as of 09:04, 15 April 2023

886 bytes removed ,  1 year ago
→‎{{header|Go}}: Updated in line with Wren example of which it is a translation.
(→‎{{header|Wren}}: Further speed-up.)
(→‎{{header|Go}}: Updated in line with Wren example of which it is a translation.)
Line 718:
=={{header|Go}}==
{{trans|Wren}}
{{libheader|Go-rcu}}
<syntaxhighlight lang="go">package main
 
import "fmt"(
}"fmt"▼
 
for {"rcu"▼
func sieve(limit int) []bool {
)
limit++
// True denotes composite, false denotes prime.
c := make([]bool, limit) // all false by default
c[0] = true▼
c[1] = true
for i := 4; i < limit; i += 2 {
c[i] = true▼
▲ }
p := 3 // Start from 3.
▲ for {
p2 := p * p▼
if p2 >= limit {
break▼
}
for i := p2; i < limit; i += 2 * p {
c[i] = true
}
for {
p += 2
if !c[p] {
break
}
}
}
return c
}
 
func commatize(n int) string {
s := fmt.Sprintf("%d", n)
if n < 0 {
s = s[1:]
}
le := len(s)
for i := le - 3; i >= 1; i -= 3 {
s = s[0:i] + "," + s[i:]
}
if n >= 0 {
return s
}
return "-" + s
}
 
func main() {
limit := int(1e6)
clowerLimit := sieve(limit - 1)2500
c := rcu.PrimeSieve(limit-1, true)
var erdos []int
lastErdos := 0
▲ c[0]ec := true0
for i := 2; i < limit; {
if !c[i] {
Line 781 ⟶ 745:
}
if found {
erdosif =i append(erdos,< i)lowerLimit {
erdosLower erdos = append(erdosLowererdos, ei)▼
▲ c[i] = true }
▲ break lastErdos = i
▲ p2 := p * p ec++
}
}
Line 790 ⟶ 758:
}
}
fmt.Printf("The %d Erdős primes under %s are\n", len(erdosLowererdos), commatizercu.Commatize(lowerLimit))▼
lowerLimit := 2500
rcu.PrintTable(erdos, 10, 6, false)
var erdosLower []int
fmt.Printf("\n\nThe %s Erdős prime is %s.\n", commatizercu.Commatize(showec), commatizercu.Commatize(erdos[show-1]lastErdos))▼
for _, e := range erdos {
if e < lowerLimit {
▲ erdosLower = append(erdosLower, e)
} else {
break
}
}
▲ fmt.Printf("The %d Erdős primes under %s are\n", len(erdosLower), commatize(lowerLimit))
for i, e := range erdosLower {
fmt.Printf("%6d", e)
if (i+1)%10 == 0 {
fmt.Println()
}
}
show := 7875
▲ fmt.Printf("\n\nThe %s Erdős prime is %s.\n", commatize(show), commatize(erdos[show-1]))
}</syntaxhighlight>
 
Line 813 ⟶ 766:
<pre>
The 25 Erdős primes under 2,500 are
2 101 211 367 409 419 461 557 673 709
769 937 967 1009 1201 1259 1709 1831 1889 2141
2221 2309 2351 2411 2437
 
The 7,875 Erdős prime is 999,721.
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