Binary Tree Level Order Traversal II

/** * Definition for binary tree * 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> > ret;if(0==root)return ret;int nextLevelNodeNum=1;queue<TreeNode *> q;q.push(root);TreeNode *pNode=0;while(!q.empty()){int levelNodeNum=nextLevelNodeNum;nextLevelNodeNum=0;vector<int> levelNode;for(int i=0;i<levelNodeNum;i++){pNode=q.front();q.pop();levelNode.push_back(pNode->val);if(pNode->left){nextLevelNodeNum++;q.push(pNode->left);}if(pNode->right){nextLevelNodeNum++;q.push(pNode->right);}}ret.push_back(levelNode);}reverse(ret.begin(),ret.end());return ret;    }};