Balanced Binary Tree

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.

平衡二叉树Balanced binary tree的定义是：任意节点的左子树的高度和右子树的高度之差小于等于1. 那么一个二叉树是平衡二叉树 当且仅当 (1. 左子树是平衡二叉树, 2. 右子树是平衡二叉树; 3, 左右子树的高度之差小于等于1)

public boolean isBalanced(TreeNode root) {
   if (getMaxDepth(root) == -1) {
       return false;
   }
   return true;
}

public int getMaxDepth(TreeNode node) {
    if (node == null) {
        return 0;
    }
    int left = getMaxDepth(node.left);
    int right = getMaxDepth(node.right);
    if (left == -1 || right == -1 || Math.abs(left - right) > 1) {
        return -1;
    }
    return Math.max(left, right) + 1;
}