222. Count Complete Tree Nodes

Given a complete binary tree, count the number of nodes.

Definition of a complete binary tree from Wikipedia:

In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.

 

class Solution {
public:
    int countNodes(TreeNode* root) {
        if(!root) return 0;
        int leftlevel = 0;
        int rightlevel = 0;
        TreeNode * Rootleft = root;
        TreeNode * Rootright = root;
        while(Rootleft)
        {
            leftlevel ++ ;
            Rootleft = Rootleft->left;
        }
        
        while(Rootright)
        {
            rightlevel ++;
            Rootright = Rootright->right;
        }
        
        if(leftlevel == rightlevel) return pow(2,leftlevel) - 1;
        return countNodes(root->left) + countNodes(root->right) + 1;
    }
};