Create Print all nodes that don't have sibling

Print all nodes that don't have sibling

@@ -0,0 +1,125 @@
+//Print all nodes that don't have sibling
+
+import java.util.LinkedList; 
+import java.util.Queue; 
+import java.io.*;
+import java.util.*;
+
+class Node {
+    int data;
+    Node left;
+    Node right;
+
+    Node(int data) {
+        this.data = data;
+        left=null;
+        right=null;
+    }
+}
+
+class GfG {
+    static Node buildTree(String str) {
+        if(str.length() == 0 || str.charAt(0) == 'N') {
+            return null;
+        }
+
+        String ip[] = str.split(" ");
+        Node root = new Node(Integer.parseInt(ip[0]));
+        Queue<Node> queue = new LinkedList<>(); 
+        queue.add(root);
+        int i = 1;
+
+        while(queue.size()>0 && i < ip.length) {
+            Node currNode = queue.peek();
+            queue.remove();
+            String currVal = ip[i];
+
+            if(!currVal.equals("N")) {
+                currNode.left = new Node(Integer.parseInt(currVal));
+                queue.add(currNode.left);
+            }
+            i++;
+
+            if(i >= ip.length)
+                break;
+
+            currVal = ip[i];
+
+            if(!currVal.equals("N")) {
+                currNode.right = new Node(Integer.parseInt(currVal));
+                queue.add(currNode.right);
+            }
+            i++;
+        }
+
+        return root;
+    }
+
+    static void printInorder(Node root) {
+        if(root == null)
+            return;
+
+        printInorder(root.left);
+        System.out.print(root.data + " ");
+        printInorder(root.right);
+    }
+
+    public static void main (String[] args) throws IOException{
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int t = Integer.parseInt(br.readLine());
+
+        while(t-- > 0) {
+            String s = br.readLine();
+            Node root = buildTree(s);
+            Tree g = new Tree();
+            ArrayList<Integer> ans = g.noSibling(root);
+
+            for(Integer val : ans) 
+                System.out.print(val + " "); 
+            System.out.println();
+        }
+    }
+}
+
+class Node {
+    int data;
+    Node left, right;
+
+    Node(int item) {
+        data = item;
+        left = right = null;
+    }
+}
+
+class Tree {
+    void func(Node root, ArrayList<Integer> ans) {
+        if(root == null) {
+            return;
+        }
+
+        if(root.left == null || root.right == null) {
+            if(root.left != null) {
+                ans.add(root.left.data);
+            }
+
+            if(root.right != null) {
+                ans.add(root.right.data);
+            }
+        }
+
+        func(root.left, ans);
+        func(root.right, ans);
+    }
+
+    ArrayList<Integer> noSibling(Node node) {
+        ArrayList<Integer> ans = new ArrayList<>();
+        func(node, ans);
+        Collections.sort(ans);
+
+        if(ans.size() == 0) {
+            ans.add(-1);
+        }
+
+        return ans;
+    }
+}