CODE 23. Balanced Binary Tree

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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 ofevery node
never differ by more than 1.

public boolean isBalanced(TreeNode root) {
	// Start typing your Java solution below
	// DO NOT write main() function
	if (null == root) {
		return true;
	}
	return checkBalanced(root) != -1;
}

public int checkBalanced(TreeNode root) {
	if (null == root) {
		return 0;
	}
	int left = checkBalanced(root.left);
	int right = checkBalanced(root.right);

	if (left == -1 || right == -1) {
		return -1;
	}
	if (Math.abs(left - right) > 1) {
		return -1;
	} else {
		return Math.max(left, right) + 1;
	}
}