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 getHeight(TreeNode *root){
        if(root == NULL){
            return 0;
        }

        int left = getHeight(root->left);
        int right = getHeight(root->right);

        return max(left,right) + 1;
    }
    bool isBalanced(TreeNode* root) {
        if(root == NULL) return true;

        int l = getHeight(root->left);
        int r = getHeight(root->right);

        //edge condition
        return isBalanced(root->left)&&isBalanced(root->right)&&(abs(l-r) <= 1);
    }
};