added code to check for cycles

LCA.java

@@ -1,3 +1,6 @@
+import java.util.ArrayList;
+import java.util.List;
+
 public class LCA {
 
  //here 
@@ -72,12 +75,73 @@ public boolean search (Node root, int n1) {
  }
  else return false; 
  }
+
+
+
+
+
+
+
+
+
+
+
+ public static boolean hasCycles(DirectedGraph g) {
+ boolean[] visited = new boolean[g.V];
+ boolean[] stack = new boolean[g.V];
+
+ for (int i = 0; i < g.V; i++) {
+ if (isCyclicRecursive(i, visited, stack, g)) {
+ return true;
+ }
+ }
+ return false;
+
+ }
+ // Recursive util method which traverses graph checking for cycles
+ private static boolean isCyclicRecursive(int i, boolean[] visited, boolean[] stack, DirectedGraph graph) {
+ if (stack[i]) {
+ return true;
+ }
+ if (visited[i]) {
+ return false;
+ }
+
+ visited[i] = true;
+ stack[i] = true;
+
+ List<Integer> children = graph.adj.get(i);
+
+ for (Integer c : children) {
+ if (isCyclicRecursive(c, visited, stack, graph)) {
+ return true;
+ }
+ }
+
+ stack[i] = false;
+
+ return false;
+ }
 
-
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ /* 
  public static void main(String[] args) { 
  LCA tree = new LCA(); 
  
- /* Let us create following BST 
+ Let us create following BST 
  50 
  / \ 
  30 70 
@@ -92,7 +156,7 @@ public static void main(String[] args) {
  tree.insert(40); 
  tree.insert(70); 
  tree.insert(n1); 
- tree.insert(n2); */
+ tree.insert(n2); 
  
  int n1 = 5;
  int n2 = 14;
@@ -107,7 +171,7 @@ public static void main(String[] args) {
  Node t = tree.lca(tree.root, n1, n2); 
  System.out.println("LCA of " + n1 + " and " + n2 + " is " + t.key);
  
- } 
+ } */
  }