average_of_levels_in_binary_tree.cpp

/*
637. Average of Levels in Binary Tree
Easy
Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.

Example 1:

Input:
    3
   / \
  9  20
    /  \
   15   7
Output: [3, 14.5, 11]
Explanation:
The average value of nodes on level 0 is 3,  on level 1 is 14.5, and on level 2 is 11. Hence return [3, 14.5, 11].

Note:

    The range of node's value is in the range of 32-bit signed integer.
*/

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<double> averageOfLevels(TreeNode* root) {
        vector<double> result;
        if(root==NULL)
            return result;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()){
            int size = q.size();
            long sum = 0;
            for(int i=0;i<size;i++){
                TreeNode* curr = q.front();
                q.pop();
                sum += curr->val;
                if(curr->left!=NULL)
                    q.push(curr->left);
                if(curr->right!=NULL)
                    q.push(curr->right);
            }
            result.push_back((1.0)*(sum)/size);
        }
        return result;
    }
};