add readme for graph

Author: imteekay

computer_science/data_structures/graph/README.md

@@ -0,0 +1,13 @@
+# Graph
+
+## Breadth First Search (BFS)
+
+- Use the queue data structure to hold each vertex that needs to be visited in the future.
+- It should keep a visited data structure to store all the visited vertices.
+- Runtime: O(V+E) / V = vertices | E = edges.
+
+## Depth First Search (DFS)
+
+- Use the stack data structure or do recursive.
+- It should keep a visited data structure to store all the visited vertices.
+- Runtime: O(V+E) / V = vertices | E = edges.