c++层序遍历倒序输出

c++层序遍历倒序输出

class Solution {
public:
    vector<vector<int>> levelOrderBottom(TreeNode* root) {
        vector<vector<int>> res;
        int j=0;
        queue<TreeNode*> k;
        while(root==NULL)
        {
            return res;
        }
        k.push(root);
        while(!k.empty())
        {
            int len=k.size();
            vector<int> a;
            for(int i=0;i<len;i++)
            {
                TreeNode *node=k.front();
                k.pop();
                a.push_back(node->val);
                j++;
               if(node->left!=NULL) k.push(node->left);
               if(node->right!=NULL) k.push(node->right);
            }
            res.push_back(a);
        }
         reverse(begin(res), end(res));  //调用reverse函数将容器中元素倒叙存储
        return res;
    }
};