Binary Tree Level Order Traversal

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
 #include <queue>

class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        vector<vector<int>> result;
        if(!root)
            return result;

        TreeNode* node = nullptr;
        queue<TreeNode*> q;
        q.push(root);
        q.push(nullptr);

        vector<int> v;
        while(!q.empty())
        {
            node = q.front();
            q.pop();

            if(q.empty()) {
                result.push_back(v);
                break;
            }

            if(node) {
                if(node->left)
                    q.push(node->left);
                if(node->right)
                    q.push(node->right);
                v.push_back(node->val);
            } else {
                q.push(nullptr);
                result.push_back(v);
                v.clear();
            }
        }

        return result;
    }
};