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