public string Run()
{
var phi = Totient.UpTo(ONE_MILLION);
double max = 0;
int idx = 0;
for (int i = 1; i <= ONE_MILLION; i++)
{
var ratio = (double)i / (double)phi[i];
if (ratio > max)
{
max = ratio;
idx = i;
}
}
return(idx.ToString());
}
public string Run()
{
var phis = Totient.UpTo(TEN_MILLION);
double minRatio = double.MaxValue;
long minN = 0;
for (long i = 2; i <= TEN_MILLION; i++)
{
if (i.IsPermutationOf(phis[i]))
{
var ratio = (double)i / (double)phis[i];
if (ratio < minRatio)
{
minRatio = ratio;
minN = i;
}
}
}
return(minN.ToString());
}
public string Run()
{
var phi = Totient.UpTo(ONE_MILLION);
return(phi.Skip(2).Sum().ToString());
}
