add: GraphDeepCopy

Author: Jer3myYu

java/Graphs/GraphDeepCopy.java

@@ -0,0 +1,46 @@
+import java.util.HashMap;
+import java.util.Map;
+
+import DS.GraphNode;
+
+/*
+    // Definition of GraphNode:
+    class GraphNode {
+        public int val;
+        public List<GraphNode> neighbors;
+        public MultiLevelListNode(int val) {
+            this.val = val;
+            this.neighbors = new ArrayList<>();
+        }
+    }
+ */
+
+public class GraphDeepCopy {
+    public GraphNode graphDeepCopy(GraphNode node) {
+        if (node == null) {
+            return null;
+        }
+        Map<GraphNode, GraphNode> cloneMap = new HashMap<>();
+        return dfs(node, cloneMap);
+    }
+
+    private GraphNode dfs(GraphNode node, Map<GraphNode, GraphNode> cloneMap) {
+        // If this node was already cloned, then return this previously  
+        // cloned node.
+        if (cloneMap.containsKey(node)) {
+            return cloneMap.get(node);
+        }
+        // Clone the current node.
+        GraphNode clonedNode = new GraphNode(node.val);
+        // Store the current clone to ensure it doesn't need to be created 
+        // again in future DFS calls.
+        cloneMap.put(node, clonedNode);
+        // Iterate through the neighbors of the current node to connect  
+        // their clones to the current cloned node.
+        for (GraphNode neighbor : node.neighbors) {
+            GraphNode clonedNeighbor = dfs(neighbor, cloneMap);
+            clonedNode.neighbors.add(clonedNeighbor);
+        }
+        return clonedNode;
+    }
+}