[leetcode-110]balanced-binary-tree

balanced-binary-tree

（1过）

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.

给定一个二叉树，判断它是否是高度平衡的二叉树。

本题中，一棵高度平衡二叉树定义为：

一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过1。

示例 1:

给定二叉树 [3,9,20,null,null,15,7]

    3
   / \
  9  20
    /  \
   15   7

返回 true 。

示例 2:

给定二叉树 [1,2,2,3,3,null,null,4,4]

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4

返回 false 。

我的解法：

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class BalancedBinaryTree {

    boolean flag = true;
    public boolean isBalanced(TreeNode root) {
        height(root);
        return flag;
    }
    private int height(TreeNode root) {
        if(root == null) {
            return 0;
        }
        int left = height(root.left);
        int right = height(root.right);
        if (Math.abs(left -right) >1) {
            flag = false;
        }
        return Math.max(left,right)+1;
    }
}