<T110>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.

判断一个二叉树是不是平衡二叉树，
如果这颗二叉树的左右子树之差大于1，那么该二叉树就是平衡二叉树。所以我们要写一个判断树高的方法，递归的做法如下：

/*
    struct TreeNode{
        TreeNode *left;
        TreeNode *right;
        int val;
    }
*/
class Solution{

    public:
        bool isBalanced(TreeNode *root){
            if(!root)
                return true;
            if(abs(getHeight(root->left)-getHeight(root->right)) > 1)
                return false;

            return isBalanced(root->left) && isBalanced(root->right);
        }
        // 判断树高 
        int getHeight(TreeNode *node){
            if(!node)
                return 0;
            return max(getHeight(node->left), getHeight(node->right))+1;

        }
};