Printing Products of n Consecutive Integers Within a Number

Question

I'm trying to right a program that will take a number and an n value and print out all the products of n consecutive digits within that number, and then print the greatest product of all of them.

For example, the output for 12345043 with constraint 3 would be:

1 x 2 x 3 = 6
2 x 3 x 4 = 24
3 x 4 x 5 = 60
4 x 5 x 0 = 0
5 x 0 x 4 = 0
0 x 4 x 3 = 0
Largest product is 60

My code performs abnormally, and for some reason prints (seemingly) random values as the product. I can't seem to see the bug so if someone could point it out that would be very welcome.

#include <iostream>
#include <string>

using namespace std;

int findProducts (string num, int cap); //Function to find all products and highest product

int main()
{
    string num = "12345043"; //Input
    int constraint = 3; //Number of multiples per equation
    int prod = findProducts(num, constraint); //Function to find all products and highest product
    cout << "The greatest product is " << prod << endl;
    return 0;
}

int findProducts (string num, int cap) //Function to find all products and highest product
{
    int product = 1; //Product
    int max = 0; //Variable to keep track of largest product
    for (int i = 0; i < num.length() - (cap - 1); i++) //Loop to go through all numbers in string input
    {
        for (int j = 0; j < cap; j++) //Loop through until the number of variables printed is equal to the constraint
        {
            product*=num[i + j]; //Make product equal to itself times num[i + j]
            cout << num[i + j];
            if (j != cap - 1) //If statement to cap extraneous x's being printed
            {
                cout << " x ";
            }
        }
        cout << " = " << product << endl;
        if (max < product) //If statement to check if the new product is the highest product
        {
            max = product;
        }
        product = 1; //Reset product
    }
    return max; //Return the highest product
}

Here is my output with the code above:

1 x 2 x 3 = 124950
2 x 3 x 4 = 132600
3 x 4 x 5 = 140556
4 x 5 x 0 = 132288
5 x 0 x 4 = 132288
0 x 4 x 3 = 127296
The greatest product is 140556

As you can see, very improper outputs.

Once again, any help would be much appreciated.

Thanks, Tristan

Answer 1

The problem is that you're multiplying product by a char corresponding to a digit in the input string:

product *= num[i + j];

You have to convert that char to the corresponding digit first. You can do this with something like that:

product *= num[i + j] - '0';

I tested it and after that change, the program gives the correct output.