# [102. Binary Tree Level Order Traversal](https://leetcode.com/problems/binary-tree-level-order-traversal/) # 思路 层序遍历二叉树。已经在[107题题解](https://github.com/ShusenTang/LeetCode/blob/master/solutions/107.%20Binary%20Tree%20Level%20Order%20Traversal%20II.md)分析过了。 时空复杂度均O(n) # C++ ``` C++ class Solution { public: vector> levelOrder(TreeNode* root) { vector>res; if(root == NULL) return res; queueq; TreeNode *p; q.push(root); while(!q.empty()){ vectorlevel; for(int i = q.size(); i > 0; i--){ p = q.front(); q.pop(); level.push_back(p -> val); if(p -> left) q.push(p -> left); if(p -> right) q.push(p -> right); } res.push_back(level); } return res; } }; ```