【Count Complete Tree Nodes】cpp

题目：

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.

代码：

/**

 * 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 ) return ;

            int hl = ;

            TreeNode* l = root->left;

            int hr = ;

            TreeNode* r = root->right;

            while ( l ){

                ++hl;

                l = l->left;

            }

            while ( r ){

                ++hr;

                r = r->right;

            }

            if ( hr==hl ) return pow(, hr)-;

            return Solution::countNodes(root->left) + Solution::countNodes(root->right) + ;

    }

};

tips：

学习大神的递归代码：http://bookshadow.com/weblog/2015/06/06/leetcode-count-complete-tree-nodes/

（1）如果left height=right height则是full tree可以直接返回节点数

（2）如果left height!=right height则不是full tree，分别递归求解left和right的节点数

巴特西

【Count Complete Tree Nodes】cpp

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