func C050() (interface{}, error) {
limit := 1000000
primes := utils.PrimesLowerThan(limit)
totalLength := len(primes)
asKeys := map[int]bool{}
for _, prime := range primes {
asKeys[prime] = true
}
max := 0
maxValue := 0
for start := 0; start < totalLength; start++ {
sum := 0
for length := 0; length < totalLength-start; length++ {
sum += primes[start+length]
if _, found := asKeys[sum]; found {
if max < length+1 {
// fmt.Println(primes[start:start+length+1], length+1, sum)
max = length + 1
maxValue = sum
}
}
if sum >= limit {
break
}
}
}
return maxValue, nil
}
func C010() (interface{}, error) {
sum := 0
for _, prime := range utils.PrimesLowerThan(2000000) {
sum += prime
}
return sum, nil
}
func C046() (interface{}, error) {
upperLimit := 10000
// prepare maps
primes := utils.PrimesLowerThan(upperLimit)
primesMap := map[int]bool{}
twiceSquareMap := []int{}
for i := 1; ; i++ {
twiceSquare := 2 * i * i
if twiceSquare > upperLimit {
break
}
twiceSquareMap = append(twiceSquareMap, twiceSquare)
}
for _, prime := range primes {
primesMap[prime] = true
}
// bruteforce
for i := 3; i < upperLimit; i++ {
if i%2 == 0 {
// skipping even numbers
continue
}
if primesMap[i] {
// skipping prime numbers
continue
}
found := false
for _, prime := range primes {
if found {
break
}
if prime > i {
break
}
for _, twiceSquare := range twiceSquareMap {
sum := prime + twiceSquare
// fmt.Printf("%d <-> %d+%d=%d\n", i, prime, twiceSquare, sum)
if sum == i {
found = true
break
}
if sum > i {
break
}
}
}
if !found {
return i, nil
}
}
return nil, fmt.Errorf("no such odd composide number bellow %d", upperLimit)
}
func C041() (interface{}, error) {
max := 0
upperLimit := 987654321
primes := utils.PrimesLowerThan(upperLimit)
for _, prime := range primes {
if utils.IsPandigital(strconv.Itoa(prime)) {
if prime > max {
max = prime
// fmt.Println(prime)
}
}
}
return max, nil
}
func C037() (interface{}, error) {
sum := 0
for _, prime := range utils.PrimesLowerThan(1000000) {
if prime < 10 {
continue
}
primeStr := strconv.Itoa(prime)
ok := true
for i := 1; i < len(primeStr); i++ {
if !isStrPrime(primeStr[i:]) || !isStrPrime(primeStr[:i]) {
ok = false
break
}
}
if !ok {
continue
}
sum += prime
}
return sum, nil
}
func C007() (interface{}, error) {
// FIXME: use another method
primes := utils.PrimesLowerThan(1000000)
return primes[10000], nil
}