scanf() acting more than weird

Please post compilable code that you had problems with. I could not compile due to the "...". Regards.

It is a bit bigger code. It also includes set. But program exits before it gets to use set.
The for loop isnt exited correctly. I also put printf() after the scanf() within the for loop and it doesnt get printed when scanf() is called for the last time.

#include<cstdio>
#include<vector>
using namespace std;
vector<int> storage;
int main(void)
{
storage.reserve(20);
int maxcount; //never greater than 20
scanf("%d",&maxcount);
for(int i=0; i<maxcount; ++i)
{
int value;
scanf("%d",&value);
storage.push_back(value);
}
printf("INPUT WAS SUCCESSFUL\n");
return 0;
}
I have tried runing this code only and it works. Wonder why. Perhaps only other things being there makes the code unstable. I'll have to into it tomorrow. I should prepare for maths tomorrow. (City contest, jeee)

I also tried cout << "something" << endl; which flushes the buffer

The problem: The task was to write a program that takes N and then N integers (which I store in vector). My task is to calculate all possible sums based on those integers. As you can see below, I use brute force (with recursion) method to get the sums and then I store sums in the set (to eliminate duplicates). Easy thing, but I don't know what went wrong...
Here's the complete code:
#include<cstdio>
#include<vector>
#include<set>
using namespace std;
vector<int> storage;
set<int> combinations;
int sum;
int total_combinations;
int max_coins;

void make_combinations(int coins)
{
if(coins==max_coins)
{
if(combinations.insert(sum).second==true) ++total_combinations;
return;
}
for(unsigned int v=0; v!=storage.size(); ++v)
{
sum+=storage.at(v);
make_combinations(++coins);
sum-=storage.at(v);
}
return;
}

int main(void)
{
storage.reserve(20);
int maxcount; //never greater than 20
scanf("%d\n",&maxcount);
for(int i=0; i<maxcount; ++i)
{
int value;
scanf("%d",&value);
storage.push_back(value);
}
printf("INPUT OK\n");
for( int j=1; j<=maxcount; ++j)
{
sum=0;
max_coins=j+1;
make_combinations(1);
}
printf("%d\n",total_combinations);
return 0;
}

scanf is not a problem with your code.
But, you have an infinite recursion, which loops until the stack overflows (Windows displays a pretty, very informative, message box).

Your program has two bugs:
1st: The recursive call make_combinations(++coins) should be make_combinations(coins+1).

If there are more than one integer, with ++coins, it will make coins greater than max_coins (which is 1 at the start), at the second iteration of the for loop inside make_combinations.
Then, there will be an infinite recursion without stopping condition, because coins>max_coins.

2nd:
You allow sums done with maxcount+1 integers (because of the <= in the for loop of the main function.

Here is a more correct code:

#include<cstdio>
#include<vector>
#include<set>
using namespace std;
vector<int> storage;
set<int> combinations;
int sum;
int total_combinations;
int max_coins;

void make_combinations(int coins)
{
if(coins==max_coins)
{
if(combinations.insert(sum).second==true) ++total_combinations;
return;
}
else
{
for(unsigned int v=0; v!=storage.size(); ++v)
{
sum+=storage.at(v);
make_combinations(coins+1);
sum-=storage.at(v);
}
}
return;
}

int main(void)
{
int maxcount; //never greater than 20
scanf("%d\n",&maxcount);
storage.reserve(maxcount);
for(int i=0; i<maxcount; ++i)
{
int value;
scanf("%d",&value);
storage.push_back(value);
}
printf("INPUT OK\n");
for( int j=1; j<maxcount; ++j)
{
sum=0;
max_coins=j+1;
make_combinations(1);
}
printf("%d\n",total_combinations);
return 0;
}

Also, I don't like much the idea of making the "coins" variable begin with the value 1.
You need to make max_coins=j+1, which is not very intuitive and perhaps leaded to the error of the "<=" comparison.

So, it could be better to use that:

max_coins=j;
make_combinations(0);

PS: I am not sure what you mean by "all sums", but currently, for a set such as {1 ,7,5}, it includes 1 , 1+1, and 1+1+1 and many sums where a number appear twice or three times.
If you don't want to include them, then you should use a correct algorithm, knowing that it is as simple as counting in binary format (1 meaning that the number is included in the sum, and zero meaning that the number is not included in the sum), I let you find the solution : It is easy with a recursion.

...
Another issue...
using the bitset function to_string().
I won't compile complaining that there is no matching function to call.

see ...

http://www.dev-archive.com/forum/showthread.php?t=369956

It seems like different compilers require different syntax.

I use both. When I know the the type of input certainly and need every ms of CPU time, I use scanf(), when not so, or when I don't wanna bother with all that writing :).

@Philip: Thanks a lot for the link. Just what I needed.