An annoying problem

Dakar · 2004-05-10T16:54:42

I've been working on a program to find factors of a number and compare it with another, and the first part (finding the factors) worked pretty well. Now, I'm trying to store them, and I have the following code: #include <iostream> #include <cstdio> #include <cstdlib> using namespace std; int *divide(int it, int *keeper); int main() //makes a divider program { int divident; int *list; int *listo; cout << "This program divides a number by several others and shows the results.\n What shall the number be?"; cin >> divident; cout << "\n"; divide(divident, list); cout << list[1]; // to make sure it works system("PAUSE"); return 0; } int divide(int it, int *keeper) { int divider, i; for (divider=1; divider <= it; divider++) { if (!(it % divider))// this was suggested by leiavoia. keeper[i] = (it/divider); cout << (it/divider) << " "; i++; } cout << "\n"; // cout << "Press ENTER to continue..." << endl; // getchar (); return keeper; } The problem is, when I run it, windows generates an error and stops running it. Is this a problem with my code, my compiler (Dev-C++) or the OS itself? (I'm using Windows 2000) Thanks! ~Dakar [edited by - Dakar on May 7, 2004 4:11:50 PM]

For Beginners

Started by Dakar May 07, 2004 03:08 PM

12 comments, last by Zahlman 19 years, 11 months ago

Dakar

182

Author

May 09, 2004 08:17 PM

I've found the problem... I was using fac2 twice. Now it simply does not display anything.

Does anybody know what I'm doing wrong?

EDIT: Now I think I see (possibly one of) the problem(s). The loops keep on going until the end of the array, which is MUCH farther than the last occupied slot. Still, I don't now how to fix this. Help?

~Thanks
Dakar.

[edited by - Dakar on May 9, 2004 9:27:13 PM]

Zahlman

1,682

May 10, 2004 12:12 AM

The loop does not go "to the end of the array"; it goes until the first zero-valued element. If nothing in your array is zero (quite possible; the unused memory is uninitialized and could hold anything), then you have a crash (access violation). What you need to do is remember the count of how many elements are meaningful in there.

Or, you could just use the property that the common factors of two numbers are simply the factors (including itself) of the greatest common factor of the two numbers. Note that there is a well known algorithm for finding GCD''s.

Again, strongly consider std::vector. It will keep track of this resizing/knowing-current-size business for you.

Also, you passed "list" to the factor-finding function the second time as well; I assume you meant to pass "listo" so as to have two separate sets of data to compare.

Also, "real" is a strange name for that function.

Dakar

182

Author

May 10, 2004 07:23 AM

quote:Original post by Zahlman
The loop does not go "to the end of the array"; it goes until the first zero-valued element. If nothing in your array is zero (quite possible; the unused memory is uninitialized and could hold anything), then you have a crash (access violation). What you need to do is remember the count of how many elements are meaningful in there.

Thanks, I''ve now made sure the last needed array space is null.

quote:Or, you could just use the property that the common factors of two numbers are simply the factors (including itself) of the greatest common factor of the two numbers. Note that there is a well known algorithm for finding GCD''s.

I see. I''ll try and work that in.

quote:Again, strongly consider std::vector. It will keep track of this resizing/knowing-current-size business for you.

Also, you passed "list" to the factor-finding function the second time as well; I assume you meant to pass "listo" so as to have two separate sets of data to compare.

Also, "real" is a strange name for that function.

Sorry, but I don''t know what a vector is in C++.

The list thing was the problem. Now it works perfectly. Thanks!

Real was short for "Realize", though I have no idea why I wanted it to be calld that. I changed its name to factor.

Thanks again!
~Dakar.