Time Cost

13min30s

Code

/**
 * 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:
    vector<vector<int>> levelOrder(TreeNode* root) {
        vector<vector<int>> result;
        if (root == nullptr) return result;
        vector<int> tmp;
        queue<TreeNode*> q;
        q.push(root);
        int current_size = q.size();
        while (current_size > 0) {
            while (current_size > 0) {
                TreeNode* current = q.front();
                q.pop();
                tmp.push_back(current->val);
                current_size--;
                if (current->left != nullptr) q.push(current->left);
                if (current->right != nullptr) q.push(current->right);
            }
            result.push_back(tmp);
            tmp.clear();
            current_size = q.size();
        }

        return result;
    }
};