Question

I’m currently building a converter in C#. My program is converting from/to Decimal, Binary and Hexadecimal. My problem is that in some specific cases the result is not correct.

Examples:

FFFFF (hexa) to Decimal = 148575 (Real answer: 1048575)

20000 (decimal) to Decimal = 20 (Real answer: dont need a calculator :P)

Also I can’t use any Convert.ToString as it is for school and my teacher asked us to manipulate the variables and play with functions.

I think my convertToString() function causes the problem of losing zeros somewhere.

private string convertToString(int value)
{
    string result = "";
    string tmp = "";
    int y = 0;

    while (value != 0) {
        int valeur = value;
        y = 0;
        while (valeur > 9) {
            valeur = valeur / 10;
            y++;
        }
        switch (valeur) {
            case 0:
                tmp = "0";
                break;
            case 1:
                tmp = "1";
                break;
            case 2:
                tmp = "2";
                break;
            case 3:
                tmp = "3";
                break;
            case 4:
                tmp = "4";
                break;
            case 5:
                tmp = "5";
                break;
            case 6:
                tmp = "6";
                break;
            case 7:
                tmp = "7";
                break;
            case 8:
                tmp = "8";
                break;
            case 9:
                tmp = "9";
                break;
        }
        value = (int)(value - (valeur * Math.Pow(10, y)));
        result = result + tmp;
    }

    if (y != 0) {
        result = result + "0";
    }
    return result;
}

Thank you in advance.

Answer 1

The problem is that you create confusion with two names meaning the same in English and French: value / valeur;

You would calculate the decimal places like this

string result = "";
bool minus = false;
if (value == 0 ) {
    result = "0";
} else {
    // Begin the string with a minus (`-`) if value is negative
    // and continue the conversion with a positive value.
    if (value < 0) {
         minus = true;
         value = - value;
    }

    // Add decimals to the result as long as the remaining number is not zero.
    while (value > 0) { 
        // Get last decimal using the modulo operator
        int lastDecimal = value % 10;

        // Prepend the decimal to the result after having converted it to a character
        result = (char)('0' + lastDecimal) + result;

        // Divide the value by 10. Integer division!
        value = value / 10;
    }
    if (minus) {
        result = "-" + result;
    }
}