EPI clone graph

Author: Dhananjay Nagargoje

Diff for: src/main/java/problems/ongraph/GraphClone.java

@@ -0,0 +1,42 @@
+package problems.ongraph;
+
+
+import java.util.*;
+
+public class GraphClone {
+
+    public static class GraphVertex {
+        public int label;
+        public List<GraphVertex> edges;
+
+        public GraphVertex(int label) {
+            this.label = label;
+            edges = new ArrayList<>();
+        }
+    }
+
+    public static GraphVertex cloneGraph(GraphVertex graph) {
+
+        if (graph == null) {
+            return null;
+        }
+
+        Map<GraphVertex, GraphVertex> vertexMap = new HashMap<>();
+        Queue<GraphVertex> q = new ArrayDeque<>();
+        q.add(graph);
+        vertexMap.put(graph, new GraphVertex(graph.label));
+        while (!q.isEmpty()) {
+            GraphVertex v = q.remove();
+            for (GraphVertex e : v.edges) {
+                // Try to copy vertex e.
+                if (vertexMap.putIfAbsent(e, new GraphVertex(e.label)) == null) {
+                    q.add(e);
+                }
+                // Copy edge.
+                vertexMap.get(v).edges.add(vertexMap.get(e));
+            }
+        }
+        return vertexMap.get(graph);
+    }
+}
+