Question

I had to design a ruler using only recursion (no loops). The user puts in the ruler length and the depth(height) of the tick marks. I managed to build this just fine using simple for and while loops, but when I tried to translate it into recursion, I am having some trouble. I get a stack overflow and first chance exception at the end of running the file, BUT, just before the error kills it, I get the correct output. I’ve been using the test cases length: 4 and depth: 5, and length: 12 and depth: 3.

If anyone has an idea of how much I screwed up my recursive effort, I’m all ears.

#include <iostream>
#include <string>

using namespace std;
void solve (int, int, int, string, int);

int main()
{
    int depth, length;
    cout << "Enter a ruler length: ";
    cin >> length;
    cout << endl << "Enter a marking depth: ";
    cin >> depth;

    int i = 0;
    string ruler = "";
    int size = length * pow(2, (depth-1));

    solve(length, depth, i, ruler, size);


    int x;
    cin >> x;

    return 0;
}

void solve (int length, int depth, int i, string ruler, int size)
{
    if (depth > 0)
    {

        int inc = pow(2, depth-1);

        if (i <= (size))
        {   
            if (i % inc == 0) {
                cout << "|";
            }

            if (i % inc != 0) {
                cout << " ";                
            }

            solve (length, depth, ++i, ruler, size);


        }
        cout << "\n";

    }

    solve (length, depth-1, 0, ruler, size);    
}

Answer 1

You need a return point from solve recursion function, like:

void solve (int length, int depth, int i, string ruler, int size)
{

    if (depth > 0)
    {
        int inc = pow(2, depth-1);

        if (i <= (size))
        {   
            if (i % inc == 0) {
                cout << "|";
            }

            if (i % inc != 0) {
                cout << " ";                
            }

            solve (length, depth, ++i, ruler, size);
        }
        cout << "\n";            
    }
    else
    {
         return; //<<<---- return out  
    }

    solve (length, depth-1, 0, ruler, size);    
}