product of digits in a number

I want to print the the product of digits in a number using the following code. Plz view the following code and find me the error in it and help me to solve it in 2 different ways using static method and also in general manner using do while loop in the main method

namespace Prime2

{

class ProdOfDigits

{

public static double evalulate(double no)

{

if (no == 0) return 0;

double temp = 1;

{

temp = (no % 10) * temp;

no = no / 10;

} while (no > 0);

return temp;

}

static void Main(string[] args)

{

double num,rem,temp=1;

Console.WriteLine("Enter the Number to find the Product of Digits ");

num = double.Parse(Console.ReadLine());

/* do

{

// rem = num % 10;

//temp = rem * temp;

temp = (num % 10) * temp;

num = num / 10;

} while (num>0);*/

/*if (rem==0)

Console.WriteLine("Product of Digits in Number is Zero");*/

Console.WriteLine("Product of Digits in Number is {0}", ProdOfDigits.evalulate(num));

}

You can't extract the digits from a double in the same way as you can an integer i.e. by successively dividing by 10 until zero is reached.

This is because there may be digits both before and after the decimal point.

Worse still, since doubles do not have an exact representation in the machine, dividing by ten may actual change the digits. For example, instead of 3 you might get 2.9999998879.

It's therefore best to convert the double to a string and extract the digits from that:

using System;

namespace Prime2

{

class ProdOfDigits

{

public static long evaluate(string no)

{

// if no contains a zero or uses Scientific notation return zero

if (no.Contains("0") || no.Contains("E") || no.Contains("e"))

return 0;

no = no.Replace(".", "").Replace("-", "");

long product = 1;

foreach(char c in no)

{

product *= c - 48; // '0' has ascii value of 48

}

return product;

}

static void Main(string[] args)

{

Console.Write("Enter the Number to find the Product of Digits ");

string number = Console.ReadLine();

// make sure it does represent a double

double d;

bool isValid = double.TryParse(number, out d);

if (isValid)

{

// normalize the double by applying ToString() to 'd' rather than using number

// this will strip off trailing and unnecessary leading zeros

Console.WriteLine("Product of Digits in Number is {0}", evaluate(d.ToString()));

}

else

{

Console.WriteLine("Sorry, you haven't entered a valid decimal number");

}

Console.ReadKey();

}

Alternatively, you can do it all the Main() method as follows:

using System;

namespace Prime2

{

class ProdOfDigits

{

static void Main(string[] args)

{

Console.Write("Enter the Number to find the Product of Digits ");

string number = Console.ReadLine();

// make sure it does represent a double

double d;

bool isValid = double.TryParse(number, out d);

if (isValid)

{

// normalize the double by applying ToString() to 'd' rather than using number

// this will strip off trailing and unnecessary leading zeros

string no = d.ToString();

long product = 0;

// if no contains a zero or uses Scientific notation leave product as zero

if (!no.Contains("0") && !no.Contains("E") && !no.Contains("e"))

{

no = no.Replace(".", "").Replace("-", "");

product = 1;

foreach(char c in no)

{

product *= c - 48; // '0' has ascii value of 48

}

Console.WriteLine("Product of Digits in Number is {0}", product);

}

else

{

Console.WriteLine("Sorry, you haven't entered a valid decimal number");

}

Console.ReadKey();

}

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
You can't extract the digits from a double in the same way as you can an integer i.e. by successively dividing by 10 until zero is reached.

This is because there may be digits both before and after the decimal point.

Worse still, since doubles do not have an exact representation in the machine, dividing by ten may actual change the digits. For example, instead of 3 you might get 2.9999998879.

It's therefore best to convert the double to a string and extract the digits from that:

using System;

namespace Prime2
{
class ProdOfDigits
{
public static long evaluate(string no)
{
// if no contains a zero or uses Scientific notation return zero
if (no.Contains("0") || no.Contains("E") || no.Contains("e"))
return 0;
no = no.Replace(".", "").Replace("-", "");
long product = 1;

foreach(char c in no)
{
product *= c - 48; // '0' has ascii value of 48
}

return product;
}

static void Main(string[] args)
{
Console.Write("Enter the Number to find the Product of Digits ");
string number = Console.ReadLine();
// make sure it does represent a double
double d;
bool isValid = double.TryParse(number, out d);

if (isValid)
{
// normalize the double by applying ToString() to 'd' rather than using number
// this will strip off trailing and unnecessary leading zeros
Console.WriteLine("Product of Digits in Number is {0}", evaluate(d.ToString()));
}
else
{
Console.WriteLine("Sorry, you haven't entered a valid decimal number");
}

Console.ReadKey();
}
}
}

Alternatively, you can do it all the Main() method as follows:

using System;

namespace Prime2
{
class ProdOfDigits
{
static void Main(string[] args)
{
Console.Write("Enter the Number to find the Product of Digits ");
string number = Console.ReadLine();
// make sure it does represent a double
double d;
bool isValid = double.TryParse(number, out d);

if (isValid)
{
// normalize the double by applying ToString() to 'd' rather than using number
// this will strip off trailing and unnecessary leading zeros
string no = d.ToString();
long product = 0;

// if no contains a zero or uses Scientific notation leave product as zero
if (!no.Contains("0") && !no.Contains("E") && !no.Contains("e"))
{
no = no.Replace(".", "").Replace("-", "");
product = 1;

foreach(char c in no)
{
product *= c - 48; // '0' has ascii value of 48
}
}

Console.WriteLine("Product of Digits in Number is {0}", product);
}
else
{
Console.WriteLine("Sorry, you haven't entered a valid decimal number");
}

Console.ReadKey();
}
}
}
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