public static long LargestPandigitalFormedWithMultiples()
{
var pandigitals = new List <long>();
for (long i = 1; i <= 9876; i++)
{
if (PandigitalNumber.IsPandigitalWithoutZero(i))
{
var pandigitalNumber = i;
for (int j = 2; j < 10; j++)
{
pandigitalNumber = pandigitalNumber.JoinWith(i * j);
if (pandigitalNumber > 987_654_321 ||
!PandigitalNumber.IsPandigitalWithoutZero(pandigitalNumber))
{
break;
}
if (pandigitalNumber >= 123_456_789)
{
pandigitals.Add(pandigitalNumber);
break;
}
}
}
}
return(pandigitals.Max());
}
public static long ProductsSum()
{
var pandigitalProducts = new List <long>();
long sum = 0;
for (long a = 2; a <= 98; a++)
{
if (PandigitalNumber.IsPandigitalWithoutZero(a))
{
var bInit = a < 10 ? 1234 : 123;
var bThreshold = a < 10 ? 9876 : 987;
for (long b = bInit; b <= bThreshold; b++)
{
var ab = a.JoinWith(b);
if (PandigitalNumber.IsPandigitalWithoutZero(ab))
{
var product = a * b;
if (PandigitalNumber.IsPandigitalWithoutZero(product.JoinWith(ab)) &&
!pandigitalProducts.Contains(product))
{
pandigitalProducts.Add(product);
sum += product;
}
}
}
}
}
return(sum);
}