LeetCode 107. 二叉树的层次遍历 II(reverse一下即可）

二叉树的层次遍历 II

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> levelOrderBottom(TreeNode* root) {
                vector<vector<int>> ans;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()){
            int size = q.size();
            vector<int> list;
            while(size--){
                TreeNode* r =  q.front();
                q.pop();
                if(!r){
                    continue;
                }
                list.push_back(r->val);
                q.push(r->left);
                q.push(r->right);
            }
            if(list.size()){
                ans.push_back(list);
            }
            
        }
        reverse(ans.begin(),ans.end());
        return ans;
    }
};