solution: clone graph

Author: Jeongwon Na

clone-graph/njngwn.java

@@ -0,0 +1,40 @@
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public List<Node> neighbors;
+    public Node() {
+        val = 0;
+        neighbors = new ArrayList<Node>();
+    }
+    public Node(int _val) {
+        val = _val;
+        neighbors = new ArrayList<Node>();
+    }
+    public Node(int _val, ArrayList<Node> _neighbors) {
+        val = _val;
+        neighbors = _neighbors;
+    }
+}
+*/
+
+class Solution {
+    HashMap<Node, Node> nodeMap = new HashMap<>(); // key: original Node, value: copied Node
+
+    public Node cloneGraph(Node node) {
+        if (node == null) return null;
+
+        if (nodeMap.containsKey(node)) {
+            return nodeMap.get(node);
+        }
+
+        Node newNode = new Node(node.val);
+        nodeMap.put(node, newNode);
+
+        for (Node neighborNode : node.neighbors) {
+            newNode.neighbors.add(cloneGraph(neighborNode));
+        }
+
+        return newNode;
+    }
+}