LeetCode222——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 2hnodes
inclusive at the last level h.

实现：

class Solution {

public:

    int getHeight(TreeNode* root) {

        int h = 0;

        while (root) {

            root = root->left;

            h++;

        }

        return h;

    }

    int countNodes(TreeNode* root) {

        if (!root) return 0;

        int lh = getHeight(root->left);

        int rh = getHeight(root->right);

        

        if (lh == rh) 

            return pow(2, lh) + countNodes(root->right);

        return pow(2, rh) + countNodes(root->left);

    }

};