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Problem08.cs
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Problem08.cs
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namespace Miller.ProjectEuler.Solutions
{
/// <summary>
/// Largest product in a series
/// </summary>
/// <seealso cref="https://projecteuler.net/problem=8"/>
public class Problem08
{
private const string BigNumber = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450";
/// <summary>
/// Iteratively slices adjacent digits of <paramref name="length"/> from <see cref="BigNumber"/> and takes their product.
/// The greatest product is returned.
/// </summary>
/// <param name="length">The length of each slice of adjacent digits. Defualt is 13.</param>
/// <returns>
/// Returns the greatest product.
/// </returns>
public ulong Solve(int length = 13)
{
ulong greatestProduct = 0;
for (int i = 0; i < BigNumber.Length; i++)
{
if (i + length > BigNumber.Length)
{
break;
}
var slice = BigNumber.Substring(i, length);
ulong product = 1;
foreach (var digit in slice)
{
product *= ulong.Parse(digit.ToString());
}
if (product > greatestProduct)
{
greatestProduct = product;
}
}
return greatestProduct;
}
}
}