reading from file!

[ETAkoG1T]

I am making a program that reads from a file and should find the five consecutive numbers with the biggest product. I thought I this would work but it doesn't, it doesn't generate but it just waits for input. Please don't ask what the problem is because the problem is that the program I thought should work doesn't! Thanks for the time:

Code:

#include "stdafx.h"
#include <iostream>
#include <Windows.h>
#include <fstream>
using namespace std;
long product(char ar[]);

int main()
{
	long biggest = 0;
	ifstream in;
	char ar[5];
	int a = 0;
	int o = 0;
	in.open("digits.txt");
	for(int i = 0; !(in.eof());  i++  )
	{
		for(;o < 5; o++)
		in.get(ar[o]);

		if(biggest < product(ar))
			biggest = product(ar);

		in.get(ar[a]);
		if(ar[a] == '\n')
			in.get(ar[a]);
		a++;
		if(a == 5)
			a = 0;
	}
	cout << "The largest product is: " << biggest;
	cin.get();
	cin.get();
	return 0;
}

long product(char ar[])
{
	return ar[0] * ar[1] * ar[2] * ar[3] * ar[4];
}

[ETAkoG1T]

This is what the file contains:
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450


Its not homework its a project euler problem.

[ETAkoG1T]

I fixed the program but it generates wrong answer

[Vlykarye]

++[variable] for performance gain.

[Vlykarye]

for(;o < 5; o++)
     in.get(ar[o]);

By the way, you never reset o back to 0.
So I'm going to assume that your code just keeps comparing the first 5 digits.

[ETAkoG1T]

No it is meant to not reset back to 0, its only suppose to do that once, then it will only change one value every time from then on! Study the code a bit more and you will understand but the answer I get is still wrong.

[Vlykarye]

char ar[5];
ar has only 5 slots... I don't understand.. if o keeps increasing.. then where is the data going?

[ETAkoG1T]

This is the first line the program is suppose to check:
73167176531330624919225119674426574742355349194934
This is how the array checks the numbers
7 * 3 * 1 * 6 * 7
[0] [1] [2] [3] [4]
then it changes the first in the array:
3 * 1 * 6 * 7 * 1
[1] [2] [3] [4] [0]
Notice how 0 now is the new number
1 * 6 * 7 * 1 * 7
[2] [3] [4] [0] [1]
Do you notice how I use the array? I am not very good with c++ but I thought this was a cool way.
6 * 7 * 1 * 7 * 6
[3] [4] [0] [1] [2]

every time the array changes the program evaluates the product and compares it to the biggest so far.

[Vlykarye]

Oh nevermind. Sorry. I wasn't giving it all my attention.
Not sure what the problem is, though.

[ETAkoG1T]

I solved the problem, the problem was that because char values isn't the same as the integer values the calculations was with the ascii codes making the answers really big numbers. I made a convertor though so now it works :)

[Vlykarye]

Well gratz. i'll have to take a look later