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