func E40() int {
prod := 1
for i := 0; i <= 6; i++ {
prod *= d(utils.Pow(10, i))
}
return prod
}
func E124() int {
const upto = 100000
primes := utils.Primes(upto)
rad := make(TupleArray, upto+1)
for i := 1; i <= upto; i++ {
rad[i][0], rad[i][1] = i, i
}
for _, i := range primes {
for k := 2; utils.Pow(i, k) <= upto && utils.Pow(i, k) > 0; k++ {
for j := utils.Pow(i, k); j <= upto; j += utils.Pow(i, k) {
rad[j][1] /= i
}
}
}
sort.Sort(rad)
return rad[10000][0]
}
func E32() (sum int) {
products := make(map[int]bool)
// i, j = number of digits in the multiplicand, multiplier
// i + j + (i + j - 1) = 2*i + 2*j - 1 = 9 => i + j = 5
for d := 1; d < 5; d++ {
for i := utils.Pow(10, d-1); i < utils.Pow(10, d); i++ {
for j := utils.Pow(10, 5-d-1); i <= j && j < utils.Pow(10, 5-d); j++ {
if isPandigital(i, j, i*j) {
products[i*j] = true
}
}
}
}
for k, _ := range products {
sum += k
}
return sum
}