public static bool IsPandigital(int n)
{
if (n > 1000000000)
{
return(false);
}
int[] nums = MiscFunctions.DigitsFromInt(n);
int[] dig = new int[nums.Length];
for (int i = 0; i < dig.Length; i++)
{
dig[i] = i + 1;
}
return(nums.OrderBy(x => x).ToArray().SequenceEqual(dig));
}
public static List <int> rotations(int n)
{
List <int> rots = new List <int>();
List <int> startingint = MiscFunctions.DigitsFromInt(n).ToList();
rots.Add(n);
for (int i = 1; i < startingint.Count; i++)
{
startingint.Add(startingint[0]);
startingint.RemoveAt(0);
rots.Add(MiscFunctions.ListToInt(startingint));
}
return(rots);
}
public static int DigitFifthPowers(int n)
{
List <int> digits = new List <int>();
int limit = (int)Math.Pow(10, n) * 100;
for (int i = 2; i < limit; i++)
{
int[] arr = MiscFunctions.DigitsFromInt(i);
if (PowerSum(arr, n) == i)
{
digits.Add(i);
}
}
return(digits.Sum());
}
public static double CancelOutSameDigit(int a, int b)
{
List <int> digitsa = MiscFunctions.DigitsFromInt(a).ToList();
List <int> digitsb = MiscFunctions.DigitsFromInt(b).ToList();
List <int> intersect = digitsa.Intersect(digitsb).ToList();
if (intersect.Count == 1)
{
digitsa.Remove(intersect[0]);
digitsb.Remove(intersect[0]);
if (digitsb[0] != 0)
{
return((double)digitsa[0] / (double)digitsb[0]);
}
}
return(0);
}
public static int DigitFactorials(int n)
{
int sum = 0;
CombinatoricFunctions.generatefactorial(10);
for (int i = 3; i < n; i++)
{
int[] digits = MiscFunctions.DigitsFromInt(i);
BigInteger tempsum = 0;
foreach (int digit in digits)
{
tempsum += CombinatoricFunctions.factorial(digit);
}
if (tempsum == i)
{
sum += i;
}
}
return(sum);
}
public static int PandigitalProducts()
{
HashSet <int> products = new HashSet <int>();
for (int i = 1; i < 5000; i++)
{
for (int j = 1; j < 5000; j++)
{
List <int> tempdigits = new List <int>();
tempdigits.AddRange(MiscFunctions.DigitsFromInt(i));
tempdigits.AddRange(MiscFunctions.DigitsFromInt(j));
tempdigits.AddRange(MiscFunctions.DigitsFromInt(i * j));
if (MiscFunctions.IsPandigital(tempdigits))
{
products.Add(i * j);
}
}
}
return(products.Sum());
}
