LeetCode题解之Binary Tree Level Order Traversal II

1、题目描述

2、题目分析

先遍历，再反转。

3、代码

 vector<vector<int>> levelOrderBottom(TreeNode* root) {
         vector<vector<int>> ans;
         if (root == NULL)
             return ans;

         queue<TreeNode*> q;
         q.push(root);
         vector<int> v;
         while (!q.empty()) {
             int size = q.size();
             for (int i = ; i < size; i++) {
                 TreeNode *node = q.front();
                 q.pop();
                 v.push_back(node->val);
                 if (node->left != NULL)
                     q.push(node->left);

                 if (node->right != NULL)
                     q.push(node->right);
             }
             ans.push_back(v);
             v.clear();
         }

         reverse(ans.begin(), ans.end());
         return ans;
     }