题目描述

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.

分析

判断二叉树是否平衡，规则如下：

左子树深度和右子树深度相差不大于1

核心代码：

        return Math.abs(height(root.left) - height(root.right)) <= 1
                && isBalanced(root.left) && isBalanced(root.right);

代码

    public static boolean isBalanced(TreeNode root) {

        if (root == null) {
            return true;
        }

        return Math.abs(height(root.left) - height(root.right)) <= 1
                && isBalanced(root.left) && isBalanced(root.right);

    }

    static int height(TreeNode node) {

        if (node == null) {
            return 0;
        }

        return Math.max(height(node.left), height(node.right)) + 1;
    }