Easiest C++ solution (PLEASE UPVOTE)
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:O(n)\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:O(n)\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```\n/**\n * Definition for a binary tree node.\n * struct TreeNode {\n *     int val;\n *     TreeNode *left;\n *     TreeNode *right;\n *     TreeNode() : val(0), left(nullptr), right(nullptr) {}\n *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}\n *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}\n * };\n */\nclass Solution {\npublic:\n    vector<vector<int>> levelOrder(TreeNode* root) {\n        queue<TreeNode*> q;\n        vector<vector<int>>v;\n         if(!root)\n         return {};\n\n         q.push(root);\n         \n\n         while(!q.empty()){\n             vector<int>a;\n             int size=q.size();\n\n             while(size--){\n                 TreeNode* curr=q.front();\n                 q.pop();\n\n                 a.push_back(curr->val);\n                 if(curr->left)\n                 q.push(curr->left);\n\n                 if(curr->right)\n                 q.push(curr->right);\n             }\n             v.push_back(a);\n\n         }\n         return v;\n    }\n};\n```
['Tree', 'Breadth-First Search', 'Binary Tree', 'C++']