BalancedBinaryTree.java

/**
 * Given a binary tree, determine if it is height-balanced.
 * 
 * For this problem, a height-balanced binary tree is defined as a binary tree
 * in which the depth of the two subtrees of every node never differ by more
 * than 1.
 * 
 */

public class BalancedBinaryTree {
	public boolean isBalanced(TreeNode root) {
		return determine(root) >= 0 ? true : false;
	}

	private int determine(TreeNode root) {
		if (root == null) {
			return 0;
		} else {
			int leftDepth = determine(root.left);
			int rightDepth = determine(root.right);
			if (leftDepth < 0 || rightDepth < 0
					|| Math.abs(leftDepth - rightDepth) > 1)
				return -1;
			return Math.max(leftDepth, rightDepth) + 1;
		}
	}
}