Added GCD Algorithm

Greatest_common_divisor_Algo.cpp

@@ -0,0 +1,22 @@
+// Greatest Common Divisor Algorithm in recursive approach
+
+#include<bits/stdc++.h>
+using namespace std;
+
+int gcd(int firstNum, int secondNum) {
+	// firstNum%secondNum = secondNum;
+	// when secondNum divides completely to the firstNum 
+	// firstNum%secondNum = remainder 
+	if(firstNum%secondNum==0){
+		return secondNum;
+	}
+    return gcd(secondNum,firstNum%secondNum);
+}
+
+int main(){
+  int firstnum , secondnum;
+  cin>>firstnum>>secondnum;
+  cout<<gcd(firstnum,secondnum);
+
+  return 0;
+}