Average of Levels in Binary Tree.cpp

/**
 * 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) {}
 * };
 */

#include <vector>

using namespace std;


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)
    {
        if(root == nullptr) return {};
        vector<double> res;
        vector<TreeNode*> curr, next;
        curr.push_back(root);

        while(!curr.empty())
        {
            long long sum = 0;
            for(const auto& node : curr)
            {
                sum += node->val;
                if(node->left) next.push_back(node->left);
                if(node->right) next.push_back(node->right);
            }
            res.push_back(static_cast<double>(sum) / curr.size());
            curr.swap(next);
            next.clear();
        }
        return res;
    }
};