func problem62() *big.Int {
cubes := make(map[string]*entry)
one, three := big.NewInt(1), big.NewInt(3)
for i := big.NewInt(0); ; i.Add(i, one) {
x := new(big.Int).Exp(i, three, nil) // x := i**3
// Sort the digits to produce a 'canonical' representation.
key := tools.SortedString(x.String())
e, ok := cubes[key]
if !ok {
cubes[key] = &entry{1, x}
} else {
e.count++
if x.Cmp(e.min) == -1 { // x < e.min
e.min = x
}
if e.count == 5 {
return e.min
}
}
}
}
// sameDigits checks whether two ints contain the same digits.
func sameDigits(x, y int) bool {
a := tools.SortedString(strconv.Itoa(x))
b := tools.SortedString(strconv.Itoa(y))
return a == b
}
func isPerm(x, y int) bool {
a := strconv.Itoa(x)
b := strconv.Itoa(y)
return tools.SortedString(a) == tools.SortedString(b)
}