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

05_hash_tables/c++11/01_price_of_groceries.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <unordered_map>
+#include <string>
+#include <utility>
+
+using std::cout;
+using std::endl;
+
+int main() {
+    std::unordered_map<std::string, float> book = {
+        {"apple", 0.67},
+        {"milk", 1.49},
+        {"avocado", 1.49}
+    };
+
+    // print book
+    for (std::pair<std::string, float> pair : book) {
+        cout << pair.first << ": " << pair.second << "$" << endl;
+    }
+}

05_hash_tables/c++11/02_check_voter.cpp

@@ -0,0 +1,24 @@
+#include <iostream>
+#include <unordered_map>
+#include <string>
+
+using std::cout;
+using std::endl;
+
+std::unordered_map<std::string, bool> voted;
+
+void check_voter(const std::string& name) {
+    auto search = voted.find(name);
+    if (search == voted.end() || search->second == false) {
+        voted.insert({name, true});
+        cout << "Let them vote!" << endl;;
+    } else {
+        cout << "Kick them out!" << endl;
+    }
+}
+
+int main() {
+    check_voter("tom");
+    check_voter("mike");
+    check_voter("mike");
+}