Added Goldbach (prime sum)

CPP/Algorithms/Maths/gcd.cpp

@@ -0,0 +1,25 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int gcd(int a, int b)  { 
+    if (a == 0) {
+       return b; 
+    }
+    if (b == 0) {
+       return a; 
+    }
+    if (a == b)  {
+        return a; 
+    }
+    if (a > b)  {
+        return gcd(a-b, b); 
+    }
+    return gcd(a, b-a);
+ }
+
+int main() {
+    int num1 , num2;
+    cout<<"Enter 2 positive numbers : ";
+    cin>>num1>>num2;
+    cout<<"GCD of "<<num1<<" "<<num2<<" is : "<<gcd(num1 , num2);
+}

CPP/Goldbach’s conjecture.cpp

@@ -0,0 +1,41 @@
+#include <bits/stdc++.h> 
+using namespace std;
+
+
+bool isprime(int n){
+    for(int i=2;i<=n/2;++i){
+        if(n%i==0) {
+            return false;
+        }
+    }
+    return true;
+}
+
+
+int main() {
+	ios_base::sync_with_stdio(false);
+	cin.tie(0);
+	int  t;
+	cin>>t;
+	while(t--){
+	    int n,i,j,c=0;
+	    cin>>n;
+	    for(i=2;i<=n/2;i++){
+	        if(isprime(i)){
+	        	for(j=n-i;j+i>=n;j--){
+	            	if(isprime(j) and (i+j)==n){
+	                	cout<<i<<" "<<j<<endl;
+	                	c=1;
+	                	break;
+	              	}
+	          	}
+	          	if(c==1) {
+	          	 	break;
+	          	}
+	        }
+	    }
+	    if(c==0)
+	        cout<<"-1\n";
+	}
+	return 0;
+}