Question

I were asked to do an StringToInt / Int.parse function on the white board in an job interview last week and did not perform very good but I came up with some sort of solution. Later when back home I made one in Visual Studion and I wonder if there are any better solution than mine below.

Have not bothred with any more error handling except checking that the string only contains digits.

        private int StrToInt(string tmpString)
    {
        int tmpResult = 0;

        System.Text.Encoding ascii = System.Text.Encoding.ASCII;
        byte[] tmpByte = ascii.GetBytes(tmpString);

        for (int i = 0; i <= tmpString.Length-1; i++)
        {
            // Check whatever the Character is an valid digit
            if (tmpByte[i] > 47 && tmpByte[i] <= 58)
                // Here I'm using the lenght-1 of the string to set the power and multiply this to the value
                tmpResult += (tmpByte[i] - 48) * ((int)Math.Pow(10, (tmpString.Length-i)-1));
            else
                throw new Exception("Non valid character in string");

        } 

        return tmpResult;
    }

Answer 1

I think your solution is reasonably ok, but instead of doing math.pow, I would do:

tmpResult = 10 * tmpResult + (tmpByte[i] - 48);

Also, check the length against the length of tmpByte rather than tmpString. Not that it normally should matter, but it is rather odd to loop over one array while checking the length of another.

And, you could replace the for loop with a foreach statement.