```
class Solution {
public:
vector<int> largestValues(TreeNode* root) {
if(!root) return vector<int>();
vector<int> res;
queue<TreeNode*> q;
q.push(root);
while(!q.empty()) {
int largest = INT_MIN, n = q.size();
for(int i = 0; i < n; i++) {
TreeNode* cur = q.front();
q.pop();
largest = max(largest, cur->val);
if(cur->left) q.push(cur->left);
if(cur->right) q.push(cur->right);
}
res.push_back(largest);
}
return res;
}
};
```