Move headers into include folder and add single header to include all reachability algorithms

include/graph/breadth_first_tree.h

@@ -0,0 +1,28 @@
+#ifndef BREADTH_FIRST_TREE_H_
+#define BREADTH_FIRST_TREE_H_
+
+#include "digraph.h"
+
+namespace graph {
+
+template<typename T>
+class BreadthFirstTree : public Digraph<T> {
+public:
+  BreadthFirstTree() = default;
+
+  BreadthFirstTree(std::unordered_map<T, std::unordered_set<T>> G, T root)
+    : BreadthFirstTree<T>(Digraph<T>(G), root) {}
+
+  BreadthFirstTree(Digraph<T> G, T root);
+
+  T root;
+};
+
+template<typename T>
+BreadthFirstTree<T>::BreadthFirstTree(Digraph<T> G, T root) {
+  this->adjList = algo::BreadthFirstSearch<T>(G.adjList).execute(root);
+}
+
+} // namespace graph
+
+#endif