题目
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.
思路
首先，理解题目，判断是否为二叉树高度是否平衡的标准是每个节点的左右子树相差不得超过1其次，理解题目后，很容易想到这是一道典型的递归题目（ps：特别是面试的时候，二叉树和递归联系的特别多，我面试豌豆荚也是考了一个类似的题目）
AC代码
public class BalancedBinaryTree {
static class TreeNode {
public int val;
public TreeNode left;
public TreeNode right;
public TreeNode(int x) {
this.val = x;
}
}
public static boolean isBalanced(TreeNode root) {
if (root == null) return true;
int lh = getHeight(root.left);
int rh = getHeight(root.right);
if (Math.abs(lh - rh) > 1) return false;
return isBalanced(root.left) && isBalanced(root.right);
}
public static int getHeight(TreeNode root) {
if (root == null) return 0;
return Math.max(getHeight(root.left), getHeight(root.right)) + 1;
}
}