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C Program for Basic Euclidean algorithms
  • Last Updated : 04 Dec, 2018

GCD of two numbers is the largest number that divides both of them. A simple way to find GCD is to factorize both numbers and multiply common factors.

// C program to demonstrate Basic Euclidean Algorithm
#include <stdio.h>
// Function to return gcd of a and b
int gcd(int a, int b)
    if (a == 0)
        return b;
    return gcd(b % a, a);
// Driver program to test above function
int main()
    int a = 10, b = 15;
    printf("GCD(%d, %d) = %d\n", a, b, gcd(a, b));
    a = 35, b = 10;
    printf("GCD(%d, %d) = %d\n", a, b, gcd(a, b));
    a = 31, b = 2;
    printf("GCD(%d, %d) = %d\n", a, b, gcd(a, b));
    return 0;
GCD(10, 15) = 5
GCD(35, 10) = 5
GCD(31, 2) = 1

Time Complexity: O(Log min(a, b))
Please refer complete article on Basic and Extended Euclidean algorithms for more details!

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