func Run() {
var s euler.Sieve
p := 2
count := 0
// Move the closure out of the loop for efficiency. It does
// save some time.
circular := true
pcheck := func(num int) {
if !s.IsPrime(num) {
circular = false
}
}
for p < 1000000 {
circular = true
eachRotation(p, pcheck)
if circular {
// fmt.Printf("%d\n", p)
count++
}
p = s.NextPrime(p)
}
fmt.Printf("%d\n", count)
}
func familySize(sieve *euler.Sieve, base, part int) (size int) {
orig := euler.DigitsOf(base)
work := make([]int, len(orig))
size = 0
found := false
for _, d := range orig {
if d == part {
found = true
break
}
}
if !found {
return
}
for value := part; value <= 9; value++ {
copy(work, orig)
for i := range orig {
if work[i] == part {
work[i] = value
}
}
prime := euler.OfDigits(work)
if sieve.IsPrime(prime) {
size++
}
}
return
}
func Run() {
var sieve euler.Sieve
limit := 1000000
ps := sieve.PrimesUpto(limit)
longestLen := 0
longestVal := 0
for a := 1; a < len(ps); a++ {
total := 0
for b := a; b < len(ps); b++ {
total += ps[b]
if total >= limit {
break
}
if b-a+1 > longestLen && sieve.IsPrime(total) {
longestLen = b - a + 1
longestVal = total
}
}
}
fmt.Printf("%d\n", longestVal)
}
func Run() {
var sieve euler.Sieve
prime := 2
for i := 0; i < 10000; i++ {
prime = sieve.NextPrime(prime)
}
fmt.Printf("%d\n", prime)
}
func isRightPrime(s *euler.Sieve, num int) bool {
for num > 0 {
if !s.IsPrime(num) {
return false
}
num /= 10
}
return true
}
func longestSeries(sieve *euler.Sieve, a, b int) int {
for n := 0; ; n++ {
c := n*n + a*n + b
if c < 2 || !sieve.IsPrime(c) {
return n
}
}
panic("Not reached")
}
func init() {
earlyPrimes = make([]int, 10)
var sieve euler.Sieve
p := 2
for i := range earlyPrimes {
earlyPrimes[i] = p
p = sieve.NextPrime(p)
}
return
}
func isAmicable(s *euler.Sieve, a int) bool {
if a >= limit {
return false
}
b := s.ProperDivisorSum(a)
if b >= limit || a == b {
return false
}
c := s.ProperDivisorSum(b)
return a == c
}
func Run() {
var sv euler.Sieve
largest := 0
for p := 2; p < 9999999; p = sv.NextPrime(p) {
if isPandigital(p) {
largest = p
}
}
fmt.Printf("%d\n", largest)
}
func Run() {
var sieve euler.Sieve
all := make([][]euler.Factor, 0, 10000)
for a := 2; a <= 100; a++ {
for b := 2; b <= 100; b++ {
tmp := factorPower(sieve.Factorize(a), b)
all = append(all, tmp)
}
}
sort.Sort(Nodes(all))
all = unique(all)
fmt.Printf("%v\n", len(all))
}
// Return the first goldbach prime for the given number, if present.
func goldbach(sieve *euler.Sieve, number int) (result int, present bool) {
for _, p := range sieve.PrimesUpto(number) {
if p == 2 {
continue
}
_, perfect := perfect_root((number - p) / 2)
if perfect {
result = p
present = true
return
}
}
return
}
func Run() {
var s euler.Sieve
n := 9
for ; ; n += 2 {
if s.IsPrime(n) {
continue
}
_, present := goldbach(&s, n)
if !present {
break
}
}
fmt.Printf("%d\n", n)
}
func Run() {
var sieve euler.Sieve
largest := 0
largestValue := 0
for p := 7; p < 1000; p = sieve.NextPrime(p) {
size := dlog(p)
if size > largest {
largest = size
largestValue = p
}
}
fmt.Printf("%d\n", largestValue)
}
func Run() {
var sieve euler.Sieve
base := 2
for {
size := familySize(&sieve, base, 1)
if size >= 8 {
break
}
base = sieve.NextPrime(base)
}
fmt.Printf("%d\n", base)
}
func isLeftPrime(s *euler.Sieve, num int) bool {
mod := 1
for mod < num {
mod *= 10
}
for mod > 1 {
num %= mod
mod /= 10
if !s.IsPrime(num) {
return false
}
}
return true
}
func TestMR(t *testing.T) {
var sv euler.Sieve
limit := 1000000
if testing.Short() {
limit = 100000
}
for i := 2; i < limit; i++ {
b := sv.IsPrime(i)
b2 := euler.IsPrime(i, 20)
if b != b2 {
t.Errorf("Mismatch: %d (%v!=%v)", i, b, b2)
}
}
}
func Run() {
var sieve euler.Sieve
count := 0
for i := 2; ; i++ {
factors := sieve.Factorize(i)
if len(factors) == expect {
count += 1
if count == expect {
fmt.Printf("%d\n", i-expect+1)
return
}
} else {
count = 0
}
}
}
func Run() {
var s euler.Sieve
count := 0
sum := 0
p := 11
for count < 11 {
if isRightPrime(&s, p) && isLeftPrime(&s, p) {
sum += p
count++
// fmt.Printf("%d\n", p)
}
p = s.NextPrime(p)
}
fmt.Printf("%d\n", sum)
}
func Run() {
var sieve euler.Sieve
num := start
var prime int = 2
for {
if num == int64(prime) {
fmt.Printf("%d\n", prime)
break
}
// Divide out the prime as many times as possible.
for num%int64(prime) == 0 {
num /= int64(prime)
}
prime = sieve.NextPrime(prime)
}
}
func divisorCount(sieve *euler.Sieve, n int) (result int) {
result = 1
tmp := n
prime := 2
for tmp > 1 {
dcount := 0
for tmp%prime == 0 {
tmp /= prime
dcount += 1
}
result *= dcount + 1
if tmp > 1 {
prime = sieve.NextPrime(prime)
}
}
return
}
func Run() {
var sieve euler.Sieve
var result int64
// Check if this result is valid, and process it if it is.
isValid := func(nums []int) {
if nums[1]-nums[0] != nums[2]-nums[1] {
return
}
for _, num := range nums {
if !sieve.IsPrime(num) {
return
}
}
if nums[0] == 1487 {
// Skip, per problem description.
return
}
result = int64(nums[0])*100000000 + int64(nums[1])*10000 + int64(nums[0])
}
// This isn't actually right, but it so happens that the
// initial value of the result is prime. The first prime of
// the result might not be the lowest permutation, and that
// lowest permutation might not be prime.
for base := 1009; base < 10000; base++ {
if !isAscending(base) {
continue
}
perms := allPermutations(base)
selections(perms, isValid)
}
fmt.Printf("%d\n", result)
}
func isAbundant(s *euler.Sieve, n int) bool {
return s.ProperDivisorSum(n) > n
}