leetcode 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 == NULL)return 0;TreeNode*node = root;int k1(0), k2(0);while (node->left != NULL){node = node->left; k1++;}node = root;while (node->right != NULL){node = node->right; k2++;}if (k1 == k2)return pow(2, k1 + 1) - 1;return countNodes(root->left)+countNodes(root->right)+1 ;}};

accept