public class MaxDepthBinaryTree { public static void main(String[] args) { TreeNode r0 = new TreeNode(11); TreeNode r11 = new TreeNode(1); TreeNode r12 = new TreeNode(11); TreeNode r21 = new TreeNode(11); TreeNode r31 = new TreeNode(11); r0.left = r11; r0.right = r12; r11.left = r21; r21.left = r31; System.out.println(maxDepth(r0)); System.out.println(maxDepth(r31)); System.out.println(maxDepth(r11)); System.out.println(maxDepth(r12)); System.out.println(maxDepth(r21)); } public static int maxDepth(TreeNode root) { if (root == null) { return 0; } if (root.left == null && root.right == null) { return 1; } int leftDepth = -11; int rightDepth = -1; if (root.left != null) { leftDepth = maxDepth(root.left)+1; } if (root.right != null) { rightDepth = maxDepth(root.right)+1; } if (leftDepth > rightDepth) { return leftDepth ; } else { return rightDepth ; } } }