CODEWITHSUNDEEP
c#mathnumbers
user11436496
user11436496

Reputation:

How to calculate the greatest common divisor between three numbers

I have to write a program which calculates the gcd with three numbers using the euclid algorithms

I have already written the program with 2 numbers which works very well but I have no idea how can I do the same with three numbers (The big problem is it should be with the euclid algorithms)

if (z1==z2)
{
    Console.WriteLine($"The gcd of two number is {z1}");
}
else { 
    do
    {
        r = z1 % z2;
        gcd = z1;
        z1 = z2;
        z2 = r;
    } while (r != 0);
    Console.WriteLine($"The gcd of two number is {gcd}");

Upvotes: 2

Views: 1829

Answers (1)

Rufus L
Rufus L

Reputation: 37020

You can write a method that gets the GCD from 2 numbers, and after calling it with 2 numbers, continue to call it with that result and the next number until there are no more numbers left.

For example, we can write a method to get the GCD of two numbers (borrowed from this site):

public static int GCD(int first, int second)
{
    while (first != 0 && second != 0)
    {
        if (first > second) first %= second;
        else second %= first;
    }

    return first == 0 ? second : first;
}

Then we can write another method that takes in a variable number of int arguments (using a params array), which gets the result of the first 2 numbers, and then continues to update that value by passing it along with the next number to our GCD method:

public static int GCD(params int[] numbers)
{
    // Do some argument validation and return 0 or throw an exception
    if (numbers == null || numbers.Length == 0) return 0;

    // Start with the result being just the first number
    var result = numbers[0];

    // Then get the GCD of the result and the next number 
    // and store that back in the result variable
    for(int i = 1; i < numbers.Length;i++)
    {
        result = GCD(result, numbers[i]);
    }

    return result;
}

Now we can call the method with as many numbers as we like:

Console.WriteLine(GCD(9, 18, 27));              // Output: 9
Console.WriteLine(GCD(4, 8));                   // Output: 4
Console.WriteLine(GCD(25, 15, 100, 30, 9000));  // Output: 5

Upvotes: 4

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