basic union find to detect cycle in undirected graph

java/basic union find to detect cycle in undirected_graph.java

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+// basic union find to detect cycle in undirected graph
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class Main
+{
+    public static void main(String[] er)
+    {
+        int[][] ar = {
+                {0,1,1},
+                {1,0,1},
+                {1,1,0}
+        };
+
+        (new UnionFind()).findLoop(ar);
+    }
+}
+
+class UnionFind
+{
+    private Map<Integer, Node> nameMap;
+    private int[][] adjMatrix;
+
+    public void findLoop(int[][] adjMatrix)
+    {
+        this.adjMatrix = adjMatrix;
+
+        createNodes();
+
+        int nodeCount = adjMatrix.length;
+        for (int from = 0; from < nodeCount; ++from)
+        {
+            for (int to=from; to<nodeCount;++to)
+            {
+                if (adjMatrix[from][to] == 1)
+                {
+                    if (isLoop(from, to))
+                    {
+                        System.out.print("loop found in " + from + " " + to);
+                        return;
+                    }
+
+                    union(from, to);
+                }
+            }
+        }
+    }
+
+    private void union(int from, int to)
+    {
+        Node head1 = getHead(from);
+        Node head2 = getHead(to);
+
+        if (head1.nodeCount() < head2.nodeCount())
+        {
+            head2.setParent(head1);
+            head1.setNodeCount(head1.nodeCount() + head2.nodeCount());
+        }
+        else
+        {
+            head1.setParent(head2);
+            head2.setNodeCount(head1.nodeCount() + head2.nodeCount());
+        }
+    }
+
+    private Node getHead(int name)
+    {
+        Node cursor = nameMap.get(name);
+
+        while (cursor.getParent() != null)
+        {
+            cursor = cursor.getParent();
+        }
+
+        return cursor;
+    }
+
+    private boolean isLoop(int from, int to)
+    {
+        Node fromHead = getHead(from);
+        Node toHead = getHead(to);
+
+        if (fromHead.getName() == toHead.getName())
+        {
+            return true;
+        }
+
+        return false;
+    }
+
+    private void createNodes()
+    {
+        int count = adjMatrix.length;
+        nameMap = new HashMap<Integer, Node>();
+        while (count >= 0)
+        {
+            Node node = new Node(count);
+            nameMap.put(count, node);
+
+            --count;
+        }
+    }
+}
+
+class Node
+{
+    private Integer name, nodeCount;
+    private Node parent;
+
+    public Node(Integer name)
+    {
+        this.name = name;
+        nodeCount = 1;
+    }
+
+    public Integer getName()
+    {
+        return name;
+    }
+
+    public Integer nodeCount()
+    {
+        return nodeCount;
+    }
+
+    public void setNodeCount(Integer nodeCount)
+    {
+        this.nodeCount = nodeCount;
+    }
+
+    public Node getParent()
+    {
+        return parent;
+    }
+
+    public void setParent(Node parent)
+    {
+        this.parent = parent;
+    }
+}