I hate to say this, but ijk, I really need to inspect your program yourself before dumping it in a forum.
Yeah, dumping is a harsh word to use, but look at your code. What do you think you are doing ! There are so damn many many mistakes. It was really really painful to find and correct the mistakes. It would have been much easier for me to write a program for double base representation, by myself.

( This is not an article, but don't blame me if it's as long as an article; 'cuz I have to highlight the mistakes )

Mistakes :

Code:
```unsigned long bs(unsigned long a[],unsigned long d, unsigned long beg, unsigned long end, unsigned long x)
{    // WHY DOES THIS FUNC ACCEPT 'd' ??
int mid;
mid=(beg+end)/2;
if (x<a[mid])
{
end=mid-1;
bs(a,d,beg,end,x);
}
else if(x<a[mid])    //same as previous case !!!!!!!!!
{
beg=mid+1;
bs(a,d,beg,end,x);
}
else if(x>a[end])                         // This should be the 2nd IF-check.
{    cout<<a[end]<<" + ";
return a[end];
}
else if(x==a[mid])                       // This should be the first IF-check.
{
cout<<"FOUND!!\n";
return a[mid];
}
}

void alg(unsigned long a[],unsigned long d, unsigned long x)
{
unsigned long num;
num=(x-bs(a,d,0,30,x));
if (num>0)
alg(a,d,num);

}

int main()
{     // main func was missing data-type !
int c,n,d;
// 32^2 does not need unsigned long, unsigned int will do, array index should be int not long.
d=c=(unsigned long)(pow(32,2));
// array b was ABSOLUTELY un-necessary !
unsigned long a[d],b[c],t,x,y;
d=c=0;
a[0]=0;
b[0]=0;
for(int i=0;i<32;i++)
{
for(int j=0;j<32;j++)
{
b[c]=(unsigned long)(pow(2,i)*pow(3,j));
if(j==0 || ULONG_MAX/pow(3,j)>pow(2,i))
{
a[++d]=b[c++];
// cout<<i<<"\t"<<j<<"\t"<<a[d]<<endl;
}
else
{
break;
}
}
}
sort(a,a+d);
cout<<"enter element:";
cin>>x;
cout<<"its representation is :"<<endl;
alg(a,d,x);
system("PAUSE");
return 0;      // no return !
}```

Remarks :
(1) Your program is full of sh*t. You need to revise your C++ lessons.
(2) Your algo implementations are really poor. Try to implement better algo.

( Painfully) modified code:
Code: c++
`#include <iostream>#include <cmath>using namespace std;unsigned long bs(unsigned long a[], unsigned beg, unsigned end, unsigned long x){    unsigned long mid;    mid=(beg+end)/2;    if (x==a[mid])    {        cout << a[mid];        return a[mid];    }    else if (beg>end)    {        cout<<a[end]<<" + ";        return a[end];    }    else if (x<a[mid])    {        end=mid-1;        return bs(a,beg,end,x);    }    else if (x>a[mid])    {        beg=mid+1;        return bs(a,beg,end,x);    }}void alg(unsigned long a[],unsigned d, unsigned long x){    unsigned long num;    num=x-bs(a,0,d,x);    if (num>0)        alg(a,d,num);}const unsigned SIZE = 144;unsigned long a[SIZE],t,x,y;int main(){    int c,n,d;    d=c=0;    a[0]=0;    for (int i=0;i<12;i++)        for (int j=0;j<12;j++)            a[12*i+j]=(unsigned long)(pow(2.0,i)*pow(3.0,j));    sort(a,a+SIZE);    cout<<"Enter element : ";    cin>>x;    cout<<"Its representation is : "<<endl;    alg(a,SIZE-1,x);    putchar(10);    putchar(10);    system("PAUSE");    return 0;}`

Sample run :
Enter element : 655
Its representation is :
648 + 6 + 1

Enter element : 36
Its representation is :
36

Enter element : 38
Its representation is :
36 + 2

Enter element : 444
Its representation is :
432 + 12

Enter element : 555
Its representation is :
512 + 36 + 6 + 1

Enter element : 23743
Its representation is :
23328 + 384 + 27 + 4

Enter element : 25653
Its representation is :
23328 + 2304 + 18 + 3

Enter element : 1
Its representation is :
1

Enter element : 0
Its representation is :
0

I repeat again, Please inspect your program yourself before throwing it into a forum.