【LeetCode】Binary Tree Level Order Traversal

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
struct Node
{
    TreeNode* tree;
    int level;
    Node(TreeNode* root, int l):tree(root), level(l){}
};

class Solution {
public:
    vector<vector<int> > levelOrder(TreeNode *root) {
        vector<vector<int> > result;
        if(root == NULL)
            return result;
        int lastLevel = 0;
        vector<int> cur;
        queue<Node*> q;
        Node* rootNode = new Node(root, 0);
        q.push(rootNode);
        while(!q.empty())
        {
            Node* front = q.front();
            q.pop();
            if(front->level > lastLevel)
            {
                result.push_back(cur);
                cur.clear();
                lastLevel = front->level;
            }
            cur.push_back(front->tree->val);
            if(front->tree->left)
            {
                Node* leftNode = new Node(front->tree->left, front->level+1);
                q.push(leftNode);
            }
            if(front->tree->right)
            {
                Node* rightNode = new Node(front->tree->right, front->level+1);
                q.push(rightNode);
            }
        }
        //add last level
        result.push_back(cur);
        return result;
    }
};