/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int maxLevelSum(TreeNode* root) {
        if (!root) return 0;
        vector<int> temp;
        int ret = 0;
        queue<TreeNode*> q;
        q.push(root);
        while (!q.empty()) {
            queue<TreeNode*> t;
            int tt = 0;
            while (!q.empty()) {
                TreeNode* node = q.front();
                if (node->left) t.push(node->left);
                if (node->right) t.push(node->right);
                tt += node->val;
                q.pop();
            }
            temp.push_back(tt);
            if (!ret) ret = 1;
            else
                if (temp[ret-1] < tt) ret = temp.size();
            q = t;
        }
        return ret;
    }
};