Add BFS tree

algorithm/bfs.h

@@ -0,0 +1,62 @@
+#ifndef BFS_H_
+#define BFS_H_
+
+#include "graph/graph.h"
+using namespace graph;
+
+#include <algorithm>
+#include <queue>
+
+namespace algo {
+
+template<typename T>
+class BFS {
+public:
+  BFS(Graph<T> G, T root) : G(G), root(root) {}
+
+  //
+  std::map<T, std::set<T>> run();
+
+  //
+  std::map<T, bool> initExplore();
+private:
+  Graph<T> G;
+  T root;
+}; 
+
+template<typename T>
+std::map<T, bool> BFS<T>::initExplore() {
+  std::map<T, bool> graphExplore;
+  for (const auto& v : G.vertices) {
+    graphExplore[v] = false;
+  }
+  return graphExplore;
+}
+
+template<typename T>
+std::map<T, std::set<T>> BFS<T>::run() {
+  std::map<T, std::set<T>> tree;
+  std::map<T, bool> graphExplore = initExplore();
+  std::queue<T> Q;
+  Q.push(root);
+  graphExplore[root] = true;
+
+  while (!Q.empty()) {
+    const auto v = Q.front();
+    Q.pop();
+
+    for (const auto& u : G.adjMatrix[v]) {
+      if (!graphExplore[u]) {
+        graphExplore[u] = true;
+        tree[v].insert(u);
+        Q.push(u);
+      }
+    }
+  }
+
+  return tree;
+}
+
+} // namespace algo
+
+#endif