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

06_breadth-first_search/c++11/01_breadth-first_search.cpp

@@ -0,0 +1,64 @@
+#include <iostream>
+#include <unordered_map>
+#include <string>
+#include <vector>
+#include <queue>
+#include <unordered_set>
+
+using std::cout;
+using std::endl;
+
+bool is_seller(const std::string& name) {
+    return name.back() == 'm';
+}
+
+template <typename T>
+bool search(const T& name, const std::unordered_map<T, std::vector<T>>& graph) {
+    std::queue<T> search_queue;
+    std::unordered_set<T> searched;
+
+    // add all friends to search queue
+    for (auto friend_name : graph.find(name) -> second) {
+        search_queue.push(friend_name);
+    }
+
+    while (!search_queue.empty()) {
+        T& person = search_queue.front();
+        search_queue.pop();
+
+        // only search this person if you haven't already searched them.
+        if (searched.find(person) == searched.end()) {
+            if (is_seller(person)) {
+                cout << person << " is a mango seller!" << endl;
+                return true;
+            }
+            std::vector<T> friend_list = graph.find(person) -> second;
+            
+            // add all friends of a person to search queue
+            for (T friend_name : friend_list) {
+                search_queue.push(friend_name);
+            }
+
+            // mark this person as searched
+            searched.insert(person);
+        }
+    }
+
+    return false;
+}
+
+int main() {
+    std::unordered_map<std::string, std::vector<std::string>> graph;
+    graph.insert({"you", {"alice", "bob", "claire"}});
+    graph.insert({"bob", {"anuj", "peggy"}});
+    graph.insert({"alice", {"peggy"}});
+    graph.insert({"claire", {"thom", "jonny"}});
+    graph.insert({"anuj", {}});
+    graph.insert({"peggy", {}});
+    graph.insert({"thom", {}});
+    graph.insert({"jonny", {}});
+
+    std::string name = "you";
+    bool result = search(name, graph);
+    cout << "Found mango seller: " << result << endl;
+}