Balanced Binary Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int  getTreeHeight(TreeNode* root){
        if(root==NULL){
            return 0;
        }
        int lh = getTreeHeight(root->left);
        int rh = getTreeHeight(root->right);
        return lh>rh ? lh+1:rh+1;
    }
    bool isBalanced(TreeNode* root) {
        if(root==NULL){
            return true;
        }
        int lh = getTreeHeight(root->left);
        int rh = getTreeHeight(root->right);
        if(fabs(lh-rh)<=1){
            return isBalanced(root->left) && isBalanced(root->right);
        }else{
            return false;
        }
    }
};