balanced tree check

input.txt

@@ -1 +1 @@
-3,9,20,null,null,15,7
+1,2,2,3,3,null,null,4,4

src/com/dsa/trees/DepthFirstTraversal.java

@@ -4,7 +4,6 @@ import java.io.BufferedReader;
 import java.io.FileReader;
 import java.io.IOException;
 import java.util.LinkedList;
-import java.util.List;
 import java.util.Queue;
 
 public class DepthFirstTraversal {
@@ -29,6 +28,7 @@ public class DepthFirstTraversal {
                 index++;
             }
             System.out.println("MinDepth: " + minDepth(root));
+            System.out.println("isBalanced: " + isBalanced(root));
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
@@ -58,4 +58,18 @@ public class DepthFirstTraversal {
         if (rightHeight == 0) return leftHeight + 1;
         return Math.min(leftHeight, rightHeight) + 1;
     }
+
+    public static boolean isBalanced(TreeNode root) {
+        return balancedDepth(root) != -1;
+    }
+
+    public static int balancedDepth(TreeNode root) {
+        if (root == null) return 0;
+        int leftHeight = balancedDepth(root.left);
+        int rightHeight = balancedDepth(root.right);
+        if (leftHeight == -1 || rightHeight == -1) return -1;
+        int weight = Math.abs(leftHeight - rightHeight);
+        if (weight > 1) return -1;
+        return Math.max(leftHeight, rightHeight) + 1;
+    }
 }