func result() (r uint64) {
search:
for r = 3; ; r += 2 {
if euler.IsPrime(r) {
continue search
}
for i := uint64(1); 2*i*i < r; i++ {
if euler.IsPrime(r - 2*i*i) {
continue search
}
}
break
}
return r
}
func main() {
fmt.Println("Problem 7. What is the 10001st Prime?")
start := time.Now()
// Skip the number 2 so that we can use an increment of 2 and halve the set
// I know that this is brute force but..
// 1. It takes 7.1ms on my machine.
// 2. I would never calculate these primes each time if I needed them. I would pre-calculate a set up front
possibility := 3
answer := 3
count := 1
for count < 10001 {
if euler.IsPrime(possibility) {
count = count + 1
answer = possibility
}
possibility = possibility + 2
}
fmt.Printf("-->Answer: The 10,001st prime is %d\n", answer)
fmt.Printf("took=%s\n\n", time.Since(start))
}
func Run() {
primes := 0
nonPrimes := 1
size := 1
span := 0
for {
span += 2
for i := 0; i < 4; i++ {
size += span
if euler.IsPrime(size, 20) {
primes += 1
} else {
nonPrimes += 1
}
}
if primes*10 < (primes + nonPrimes) {
break
}
}
fmt.Printf("%d\n", span+1)
}
func main() {
var count uint64
for n := uint64(2); n < 1000000; n++ {
m := n
isprime := true
var ok bool
for {
if !euler.IsPrime(m) {
isprime = false
break
}
m, ok = rot(m)
if !ok {
isprime = false
break
}
if m == n {
break
}
}
if isprime {
count++
}
}
fmt.Printf("35 %d\n", count)
}
func BenchmarkMR(b *testing.B) {
for i := 0; i < b.N; i++ {
if !euler.IsPrime(131071, 20) {
b.Errorf("Prime failure: %s", 131071)
}
}
}
func main() {
var count uint64
var sum uint64
nextcandidate:
for i := uint64(11); count < 11; i++ {
d := euler.NtoD(i)
dlen := len(d)
for j := 0; j < len(d); j++ {
a := euler.DtoN(d[j:dlen])
b := euler.DtoN(d[0 : dlen-j])
if !euler.IsPrime(a) || !euler.IsPrime(b) {
continue nextcandidate
}
}
count++
sum += i
}
fmt.Printf("%d\n", sum)
}
func main() {
search:
for i := uint64(1000); i < 10000-(3330*2); i++ {
if i == 1487 {
continue search
}
if !euler.IsPrime(i) {
continue search
}
if !euler.IsPrime(i + 3330) {
continue search
}
if !euler.IsPrime(i + 2*3330) {
continue search
}
if !euler.IsPerm(euler.NtoD(i), euler.NtoD(i+3330)) {
continue search
}
if !euler.IsPerm(euler.NtoD(i), euler.NtoD(i+3330*2)) {
continue search
}
fmt.Printf("49 %d%d%d\n", i, i+3330, i+3330*2)
}
}
func main() {
var largest uint64
digits := []uint64{1, 2, 3, 4, 5, 6, 7, 8, 9}
for i := uint64(1); i <= 9; i++ {
numperms := euler.Factorial(i)
for j := uint64(0); j < numperms; j++ {
dn := euler.NthPerm(j, digits[:i])
n := euler.DtoN(dn)
if euler.IsPrime(n) && pandigital(n) {
if n > largest {
largest = n
}
}
}
}
fmt.Printf("41 %d\n", largest)
}
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 main() {
starttime := time.Now()
count := 0
for start := int64(1); difference(start, 1) <= search; start++ {
for jump := int64(1); difference(start, jump) <= search; jump++ {
if euler.IsPrime(difference(start, jump)) {
count++
fmt.Println(start, jump, difference(start, jump))
}
}
}
fmt.Println(count)
fmt.Println("Elapsed time:", time.Since(starttime))
}
func main() {
var maxn, maxa, maxb, n int
for a := -999; a < 1000; a++ {
for b := -999; b < 1000; b++ {
for n = 0; ; n++ {
q := quad(n, a, b)
if q < 0 || !euler.IsPrime(uint64(q)) {
break
}
}
if n > maxn {
maxn = n
maxa = a
maxb = b
}
}
}
fmt.Printf("27 %d\n", maxa*maxb)
}
func test(repeat string, n, d int) (N int, S int64) {
for i := 0; int64(i) < euler.Choose(int64(n), int64(d)); i++ {
indices := euler.SplitSeq(d, i)
for j := 0; int64(j) < euler.IntExp(10, int64(d)); j++ {
insertstring := strconv.Itoa(j)
for len(insertstring) < d {
insertstring = "0" + insertstring
}
merged := ""
current := 0
for index := 0; index < n; index++ {
if current < d && index == indices[d-current-1] {
merged += insertstring[current : current+1]
current++
} else {
merged += repeat
}
}
mergedint, _ := strconv.ParseInt(merged, 10, 64)
//exclude leading zeroes
if mergedint > euler.IntExp(10, int64(n)-1) {
if euler.IsPrime(mergedint) {
//fmt.Println(mergedint)
N++
S += mergedint
}
}
}
}
return
}
