Added a graph class for representing and manipulating the game data

graph.cpp

@@ -0,0 +1,36 @@
+#include "graph.h"
+
+bool Graph::vertex_present(int x, int y, int size)
+{
+    int delta = size / 2;
+
+    int x_min = x - delta;
+    int x_max = x + delta;
+    int y_min = y - delta;
+    int y_max = y + delta;
+
+    for (list<Vertex>::iterator cursor = vertices.begin();
+	 cursor != vertices.end(); cursor++)
+    {
+	Vertex v = *cursor;
+	if (((x_min >= v.x_min && x_min <= x_max) &&
+	     ((y_min >= v.y_min && y_min <= y_max) ||
+	      (y_max >= v.y_min && y_max <= y_max))) ||
+	    ((x_max >= v.x_min && x_max <= x_max) &&
+	     ((y_min >= v.y_min && y_min <= y_max) ||
+	      (y_max >= v.y_min && y_max <= y_max))))
+	    return true;
+    }
+
+	return false;
+}
+
+void Graph::add_vertex(Vertex v)
+{
+    if (vertex_present(v.x, v.y)) return;
+
+    vertices.push_back(v);
+    edges.push_back(Edge(last_vertex, v));
+    last_vertex = v;
+}
+