private static List <int> GetPrimeFactors(int num, int limit)
{
var res = new List <int>();
foreach (var prime in PrimeNumbers.GetAllPrimes())
{
if (prime > num / 2)
{
break;
}
var pow = 0;
var temp = num;
while (temp % prime == 0)
{
temp /= prime;
pow++;
}
if (pow > 0)
{
res.Add((int)(Math.Pow(prime, pow)));
if (res.Count >= limit)
{
break;
}
}
}
return(res);
}
public static int Solve(long num)
{
var primes = PrimeNumbers.GetAllPrimes((int)Math.Sqrt(num));
var res = 1;
for (var i = primes.Count - 1; i > 1; i--)
{
if (num % primes[i] == 0)
{
res = primes[i];
break;
}
}
return(res);
}
public static string Solve(int index)
{
var primes = PrimeNumbers.GetAllPrimes().Where(x => x > 1000 && x < 10000).ToList();
var primeStrings = primes.Select(x => x.ToString()).ToList();
var options = new List <List <int> >();
var considered = new HashSet <int>();
foreach (var p in primes)
{
if (considered.Contains(p))
{
continue;
}
var perms = GetPermutations(p, primeStrings);
perms.ForEach(x => considered.Add(x));
for (var a = 0; a < perms.Count; a++)
{
for (var b = a + 1; b < perms.Count; b++)
{
for (var c = b + 1; c < perms.Count; c++)
{
if (perms[c] - perms[b] == perms[b] - perms[a])
{
options.Add(new List <int> {
perms[a], perms[b], perms[c]
});
a = perms.Count;
b = perms.Count;
c = perms.Count;
}
}
}
}
}
var res = options[index].Aggregate("", (c, n) => c + n.ToString());
return(res);
}