Added gcd and lcm algos

Author: prince776

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "files.associations": {
+        "iostream": "cpp"
+    }
+}

Algorithms/Mathematical/gcd_and_lcm.cpp

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+// Implements Algorithms for GCD and LCM.
+#include <iostream>
+using namespace std;
+
+int gcd(int a, int b)
+{
+    if (b == 0)
+        return a;
+    return gcd(b, a % b);
+}
+
+int gcdExtended(int a, int b, int *x, int *y)
+{
+    // Base case.
+    if (a == 0)
+    {
+        *x = 0;
+        *y = 1;
+        return b;
+    }
+
+    int x1, y1;
+    int gcd = gcdExtended(b % a, a, &x1, &y1);
+
+    *x = y1 - (b / a) * x1;
+    *y = x1;
+
+    return gcd;
+}
+
+int lcm(int a, int b)
+{
+    return (a * b) / gcd(a, b);
+}
+
+int main()
+{
+    int a = 15, b = 20;
+    int x, y;
+    cout << "GCD of " << a << " and " << b << " is: " << gcd(b, a);
+    cout << endl;
+    cout << "GCD of " << a << " and " << b << " is: " << gcdExtended(a, b, &x, &y);
+    cout << endl;
+    cout << "LCM of " << a << " and " << b << " is: " << lcm(b, a);
+    cout << endl;
+    return 0;
+}