Thread: recursion lab exercise

i need help guys ,i cant find out how to do this programm.
------------------------
Make a program that reads two physical numbers from user (N *
)
,N and S. The program should display all unique numbers
combinations of N single digits whose sum equals S. Eg.
for N = 3 and S = 10 the program should display:
8+1+1=10
7+2+1=10
6+3+1=10
5+4+1=10
6+2+2=10
5+3+2=10
4+4+2=10
4+3+3=10


other whice If a number is out of the scope it will display
"Wrong input".

Code:

int digits(N)
{
    int i,j;
    for (i=1;i<=9;i++)
    {
        for (j=1;i<=N;j++)
        {
            if (i+9<S)
            {
                
            }
        }
    }
}
int sum ()
{
    if (n==0)
        return 0;
    else
    {


    }
}


int main()
{
    int N,S,i;
    scanf("%d,%d",&N,&S);
    
    if (N*9 <= S)
    {
        
    }
    else 
    printf("Wrong Input");
    
    for (i=1;i<=N;i++)
    {
        printf("%d",digits(N));
        printf("+");
    }
    printf("=%d",S);


    return 0;
}