222-2

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int countNodes(TreeNode* root) {
        if(root==NULL) return 0;
        TreeNode *lnode=root,*rnode=root;
        int l=0,r=0;
        while(lnode){
            l++;
            lnode=lnode->left;
        }
         while(rnode){
            r++;
            rnode=rnode->right;
        }
        if(l==r) return pow(2,l)-1;
        return countNodes(root->left)+countNodes(root->right)+1;

    }
};