637. 二叉树的层平均值

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int value) : val(value), left(nullptr), right(nullptr) {}
};
​
class Solution {
public:
    vector<double> averageOfLevels(TreeNode* root) {
        queue<TreeNode*> que;
        vector<double> result;
        if (root != nullptr) que.push(root);
        while (!que.empty()) {
            int size = que.size();
            double sum = 0;
            for (int i = 0; i < size; i++) {
                TreeNode* node = que.front();
                que.pop();
                sum += node->val;
                if (size - 1 == i) result.push_back(sum/size);
                if (node->left) que.push(node->left);
                if (node->right) que.push(node->right);
            }
        }
        return result;
    }
};