剑指 Offer 55 - II. 平衡二叉树

  1. /**
  2.  * Definition for a binary tree node.
  3.  * public class TreeNode {
  4.  *     int val;
  5.  *     TreeNode left;
  6.  *     TreeNode right;
  7.  *     TreeNode(int x) { val = x; }
  8.  * }
  9.  */
  10. class Solution {
  11.     public boolean isBalanced(TreeNode root) {
  12.         if (root == null)
  13.             return true;
  14.         return Math.abs(height(root.left) - height(root.right)) <= 1 && isBalanced(root.left) && isBalanced(root.right);
  15.     }
  17.     private int height(TreeNode root) {
  18.         if (root == null)
  19.             return 0;
  20.         return Math.max(height(root.left), height(root.right)) + 1;
  21.     }
  22. }