# Description

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

The original problem is here.

The original code is here.

# My Solution

I solve this problem in C++, as below:

``````/*
*Count Complete Tree Nodes
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<stack>
#include<vector>
#include<stdlib.h>
using namespace std;
/**
* 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 countNodes(TreeNode* root) {
if(root == NULL)
return 0;
int leftH  = leftHight(root) + 1;
int rightH = rightHight(root) + 1;
if(leftH == rightH)
return     2<<(leftH-1) - 1;
else
return countNodes(root->left) + countNodes(root->right) + 1;
}
int leftHight(TreeNode * root){
int hight = 0;
while(root->left != NULL){
root = root->left;
hight ++;
}
return hight;
}
int rightHight(TreeNode * root){
int hight = 0;
while(root->right != NULL){
root = root->right;
hight ++;
}
return hight;
}
};
``````

# Note

To solve the problem, recursion is used. If the left child and the right child have the different hight, we compute the nodes of the left and right, respectively.