完全二叉树求节点个数

222. Count Complete Tree Nodes

Medium

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

Note:

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.

Example:

Input: 1 / \ 2 3 / \ / 4 5 6 Output: 6

class Solution {
public:
    int countNodes(TreeNode* root) {
        TreeNode* LeftNode = root;
        TreeNode* RightNode = root;
        int LeftNum = 0;
        int RightNum = 0;
        while(LeftNode){
            LeftNum++;
            LeftNode = LeftNode->left;
        }
        while(RightNode){
            RightNum++;
            RightNode = RightNode->right;
        }
        if(RightNum == LeftNum){
            return pow(2,RightNum) - 1;
        }
        else{
            return countNodes(root->left) + countNodes(root->right) + 1;
        }
    }
};