Project Euler 8 in C#

Question

I am trying to solve the problem 8 of Project Euler.

The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.

73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450

Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?

Of course I do not want the answer, however I can not see how my code doesn't work.

public static long problem8()
    {
        String num1000digit = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450";
        long largest = 0;
        for (int i = 0; i < 988; i++)
        {
            int product = 1;

            String str_num = num1000digit.Substring(i, 13);
            foreach (Char character in str_num)
            {
                product = product * Int32.Parse(character.ToString());
            }

            if (product > largest)
                largest = product;
        }
        return largest;
    }

What am I missing. I am getting each character and finding the product of the 13 adjacent numbers in the 100 digits. I am also checking to see if the new product is greater than the current highest. This comes out with the answer 2091059712, but project Euler tells me my answer is wrong.

Please do not give me the solution to the problem, I just need to pointer in the direction of where I can not see it D:

Have you considered the possibility that the result is larger than the maximum size of an int in C#, so you might be getting data wrap? — Joseph James, Feb 21 '16 at 04:17

score 3 · Accepted Answer · answered Feb 21 '16 at 04:26

3

The correct answer is too large for a 32-bit integer. Try changing int product = 1; to long product = 1;.

answered Feb 21 '16 at 04:26

Kaz

721
3
15

Great thanks... why do I not get an error when the number is too large for a 32-bit integer. – Tom Hanson Feb 21 '16 at 04:50
@0014 Do you *have* to just spell out the answer? – Rawling Feb 21 '16 at 09:25
2

@TomHanson C# lets you decide whether or not to error out when this happens. It's a compiler option, but you can also [turn it on or off for blocks of code](http://stackoverflow.com/questions/20709495/what-is-the-c-sharp-checked-keyword-for). – Rawling Feb 21 '16 at 09:26

Project Euler 8 in C#

1 Answers1