add c++11 (#87)

* binary search c++

* selection sort c++11

* c++ recursive countdown

* c++ recursion

* c++ quicksort

* rename folder names to c++11

* add another version of binary_search function

* c++11 hash tables

* c++11 breadth-first search

03_recursion/c++11/01_countdown.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+
+using std::cout;
+using std::endl;
+
+void countdown(const int& i) {
+    cout << i << endl;
+    
+    // base case
+    if (i <= 0) return;\
+    
+    // recursive case
+    countdown(i - 1);
+}
+
+int main() {
+    countdown(5);
+}

03_recursion/c++11/02_greet.cpp

@@ -0,0 +1,27 @@
+#include <iostream>
+#include <string>
+
+using std::cout;
+using std::endl;
+
+void greet2(std::string name) {
+    cout << "How are you, " + name + "?" << endl;
+}
+
+void bye() {
+    cout << "Ok, bye!" << endl;
+}
+
+
+void greet(std::string name) {
+    cout << "Hello, " + name + "!" << endl;
+    greet2(name);
+    cout << "Getting ready to say bye..." << endl;
+}
+
+
+int main() {
+    greet("Adit");
+
+    return 0;
+}

03_recursion/c++11/03_factorial.cpp

@@ -0,0 +1,13 @@
+#include <iostream>
+
+using std::cout;
+using std::endl;
+
+int fact(const int& x) {
+    if (x == 1) return 1;
+    return fact(x-1) * x;
+}
+
+int main() {
+    cout << fact(5) << endl;
+}