Write a C++ program to find the smallest number that can be formed from given sum of digits and number of digits.

Find smallest number with given number of digits and sum of digits
Write a C++ program to find the smallest number that can be formed from given sum of digits and number of digits.

#include  
using namespace std;
 
// Prints the smallest possible number with digit sum 's'
// and 'm' number of digits.
void findSmallest(int m, int s)
{
    // If sum of digits is 0, then a number is possible
    // only if number of digits is 1.
    if (s == 0)
    {
        (m == 1)? cout << "Smallest number is " << 0
                : cout << "Not possible";
        return ;
    }
 
    // Sum greater than the maximum possible sum.
    if (s > 9*m)
    {
        cout << "Not possible";
        return ;
    }
 
    // Create an array to store digits of result
    int res[m];
 
    // deduct sum by one to account for cases later
    // (There must be 1 left for the most significant
    //  digit)
    s -= 1;
 
    // Fill last m-1 digits (from right to left)
    for (int i=m-1; i>0; i--)
    {
        // If sum is still greater than 9,
        // digit must be 9.
        if (s > 9)
        {
            res[i] = 9;
            s -= 9;
        }
        else
        {
            res[i] = s;
            s = 0;
        }
    }
 
    // Whatever is left should be the most significant
    // digit.
    res[0] = s + 1;  // The initially subtracted 1 is
                     // incorporated here.
 
    cout << "Smallest number is ";
    for (int i=0; i        cout << res[i];
}
 
// Driver code
int main()
{
    int s = 9, m = 2;
    findSmallest(m, s);
    return 0;
}

Output :
Smallest number is 18