public static int SumDoubleBasePalindromesUnderOneMillion()
{
var sum = 0;
for (int i = 0; i < 1_000_000; i++)
{
if (Palindrome.IsPalindrome(i) &&
new BinaryNumber(i).IsPalindrome())
{
sum += i;
}
}
return(sum);
}
public static int LargestXDigitPalindrome(int numberDigits)
{
var minNum = 1;
while (--numberDigits > 0)
{
minNum *= 10;
}
var maxNum = minNum * 10;
var largestPalindrome = 0;
for (int i = maxNum - 1; i >= minNum; i--)
{
if (i * (i - 1) <= largestPalindrome)
{
break;
}
for (int j = i - 1; j >= minNum; j--)
{
var mult = i * j;
if (mult <= largestPalindrome)
{
break;
}
if (mult > largestPalindrome && Palindrome.IsPalindrome(mult))
{
largestPalindrome = mult;
}
}
}
return(largestPalindrome);
}
