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I am trying to solve this challenge problem, where I am meant to find the GCD of two inputted numbers by referencing a function. However, I am not sure exactly where I am messing up. Here is the exact question for reference:

Write a function which accepts x and y as input parameters and calculates and returns the greatest common denominator of both values.

I tried making a function to find the GCD, and then just referencing the function later. I'm not sure what I'm doing wrong.

#include <iomanip> using namespace std; int gcd; cout << "Enter a valid integer: "; cin >> n >> m; int digit = number(n, m); return 0; } int number(int n, int m){ for (int i=1; i<=n; ++i){ int gcd = i; if(n%i==0 && m%i==0) { break; } return gcd; } }

I should be getting this: Enter two integers: 12 8 The GCD of 12 and 8 is 4.

But instead, I'm getting an error with gcd not being declared in this scope, which doesn't make sense because I declared it as an int both inside the function and outside.

**Greatest common divisor,** GCD (Greatest Common Divisor) or HCF (Highest Common Factor) of two numbers is the largest Recursive function to return gcd of a and b. Because polynomials may take many different forms, many different techniques are available for factoring them. The first method of factoring is called factoring out the GCF (greatest common factor). Example 1. Factor 5 x+ 5 y. Since each term in this polynomial involves a factor of 5, then 5 is a common factor of the polynomial. Example 2.

Easy recursive solution...try this.

int gcd(int a, int b) { if(b==0) return a; else gcd(b, a%b); }

Same can be achieved without recursion -

int gcd(int a, int b) { while(b!=0) { int tmp = a; a = b; b = tmp % b; { return a; }

Now the main function ..

#include<iostream> using namespace std; int main() { int a,b; cout<<"Enter two number: "; cin>>a>>b; cout<<"GCD of two number: "<<gcd(a,b)<<endl; }

**Program to find GCD or HCF of two numbers,** Like for many other tools on this website, your browser must be configured to allow javascript for the program to function. What is the greatest common divisor? The� When two numbers have a greatest common factor of only 1, they're called relatively prime. And that kind of makes sense because a prime number is something that only has 1 and itself as a factor. And two relatively prime numbers are numbers that only have 1 as their greatest common factor. Hope I didn't confuse you.

I hope that you are looking for something like this

#include <stdio.h> int hcf(int, int); //function declaration int main() { int a, b, result; printf("Enter the two numbers to find their HCF: "); scanf("%d%d", &a, &b); result = hcf(a, b); printf("The HCF of %d and %d is %d.\n", a, b, result); return 0; } int hcf(int a, int b) { while (a != b) { if (a > b) { a = a – b; } else { b = b – a; } } return a; }

Simple program which is easy to understand .

**GCD Calculator,** To get the GCF multiply all common factors. figure14. You can use the greatest common factor to simplify fractions. A ratio is an expression that tells us the quotient� The greatest common factor (GCF or GCD or HCF) of a set of whole numbers is the largest positive integer that divides evenly into all numbers with zero remainder. For example, for the set of numbers 18, 30 and 42 the GCF = 6.

Your function needs a little bit of tweaking to work correctly.

`gcd`

has to be defined outside the`for`

loop so it can be used as the return value.- In the
`for`

loop, using`break`

in the`if`

statement is logically incorrect. If you do that, you will always get 1 as your answer. Afer all,`n % 1`

and`m % 1`

will be zero for all values of`n`

and`m`

.

Here's an updated version that works in my tests.

int gcdfunction(int n, int m){ int gcd = 1; for (int i=1; i<=n; ++i){ if(n%i==0 && m%i==0) { gcd = i; } } return gcd; }

Please note that the Euclidean algorithm is probably the most efficient algorithm to compute the GCD of two numbers.

The Euclidean algorithm can be easily implemented using a non-recursive function too.

int gcdfunction(int n, int m){ // Make sure n is the smaller of the numbers. if ( n > m ) { std::swap(n, m); } while ( m % n != 0 ) { int next = m % n; m = n; n = next; } return n; }

**Finding the greatest common factor (Pre-Algebra, Discover fractions ,** The greatest common divisor (GCD), also called the greatest common factor, of two numbers is the largest number that divides them both. For instance, the� Your function needs a little bit of tweaking to work correctly. gcd has to be defined outside the for loop so it can be used as the return value. In the for loop, using break in the if statement is logically incorrect. If you do that, you will always get 1 as your answer. Afer all, n % 1 and m % 1 will be zero for all values of n and m.

**Greatest Common Divisor,** Two or more positive integers that have greatest common divisor 1 are said to be relatively is irrational, the resulting function is continuous at the irrationals,� GCD is also known as the greatest common factor or highest common factor. Integer mathematical function, suitable for both symbolic and numerical manipulation. GCD [ n 1, n 2, …] is the largest positive integer that divides each of the integers n 1, n 2, ….

**Greatest Common Divisor -- from Wolfram MathWorld,** The greatest common factor, or GCF, is the greatest factor that divides two numbers. To find the GCF of two numbers: List the prime factors of each number. The greatest number that is a factor of two (or more) other numbers. When we find all the factors of two or more numbers, and some factors are the same ("common"), then the largest of those common factors is the Greatest Common Factor.

**Factoring - Greatest Common Factor (GCF) - First Glance,** In mathematics, the greatest common divisor (gcd), also known as the greatest common denominator, greatest common factor (gcf), or highest common factor� Right from algebra greatest common factor calculator to linear equations, we have got all the details included. Come to Algebra-equation.com and figure out variable, completing the square and a great deal of additional algebra subject areas

##### Comments

- What are you hoping the line
`return gcd(n, m);`

would do? - That was a mistake, I just realized; I want to just print the gcd in this case of the two numbers, which would be represented by i.
- @RSahu after taking out the error in the return line and just making it become return gcd; , I still get the error that gcd is not declared.
- That error makes sense.
`gcd`

is defined in the scope of the`if`

statement. It doesn't exist outside that. - Remember that curly braces introduce a new scope. Also, the
`gcd`

in`main`

is completely unrelated to the`gcd`

in the other function. Read about lexical scope in your favourite C++ book. `int gcd(int x, int y){return y? gcd(y,x%y) : x;}`

will work too- I did a cout command, being cout << gcd; , and I get the factors of my two numbers perfectly. However, all values of i that fullfill the loop are being printed; how do I only get the highest value to get printed? If I put 12 and 20, the numbers outputted are 1, 2, and 4.
- @noviceclasscoder, print only the return value of the function, in
`main`

. After the function returns, use`std::cout << "GCD: " << variable << std::endl;`