[Tree]Count Complete Tree Nodes

Total Accepted: 22338 Total Submissions: 97234 Difficulty: Medium

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.

 (E) Closest Binary Search Tree Value

 

/**
 * 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 treeDepth(TreeNode* root)
    {
        int dep=0;
        while(root){
            dep++;
            root=root->left;
        }
        return dep;
    }
    int countNodes(TreeNode* root) {
        if(root==NULL){
            return 0;
        }
        int ldep = treeDepth(root->left);
        int rdep = treeDepth(root->right);
        if(ldep>rdep){
            return 1+countNodes(root->left) + ((1<<rdep)-1);
        }
        return 1+((1<<ldep)-1) + countNodes(root->right);
    }
};

Next challenges: (E) Closest Binary Search Tree Value