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std::gcd | C++ inbuilt function for finding GCD
  • Difficulty Level : Basic
  • Last Updated : 27 Apr, 2018

In many competitive programming problems, we need to find greatest common divisor also known as gcd. Euclids algorithm to find gcd has been discussed here

C++ has the built-in function for calculating GCD. This function is present in header file.
Syntax:

 __gcd(m, n) 
Parameter :  m, n
Return Value :  0 if both m and n are zero, 
else gcd of m and n.




// CPP program to illustrate
// gcd function of C++ STL
#include <iostream>
#include <algorithm> 
  
using namespace std;
  
int main()
{
    cout << "gcd(6, 20) = " << __gcd(6, 20) << endl;
}


Output:

gcd(6, 20) = 2

Note: If either M or N is not an integer type, or if either is (possibly cv-qualified) bool, the program is ill-formed. Also, If either |m| or |n| is not representable as a value of type std::common_type_t, the behavior is undefined.




// CPP program to illustrate
// undefined behavior of
// gcd function of C++ STL
#include <iostream>
#include <algorithm> 
  
using namespace std;
  
int main()
{
    cout << "gcd(6, 20) = " << __gcd(2.0, 8) << endl;
}


Output:
Error, As the data type float is not supported by std::gcd.



This article is contributed by Pratik Chhajer. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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