637. Average of Levels in Binary

Average of Levels in Binary Tree

[思路]：获得树每一层的平均值，使用广度优先搜索。
那么使用方法：

• 广度优先
• deque

    vector<double> averageOfLevels(TreeNode* root) {
                vector<double> res;
        deque<TreeNode*> q;
        q.push_back(root);
        while(! q.empty()){
            double temp = 0;
            int s = q.size();
            for(int i=0; i<s;i++){
                TreeNode* t=q.front();
                q.pop_front();
                if(t->left) q.push_back(t->left);
                if(t->right)q.push_back(t->right);
                temp+= t->val;
            }
            res.push_back(static_cast<double>(temp)/s);
        }
    return res;

    }