leetcode: Binary Tree Level Order Traversal

Given a binary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level).

For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ \
9 20
/ \
15 7
return its level order traversal as:
[
[3],
[9,20],
[15,7]
]
confused what “{1,#,2,3}” means? > read more on how binary tree is serialized on OJ.

/** * 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>> levelOrder(TreeNode* root) {        vector<vector<int>> vec;        queue<TreeNode*>que;        if(root == NULL)            return vector<vector<int>>(0);        TreeNode* p = root;        que.push(p);        vector<int>v;        int curCount = 1;        int nextCount = 0;        while(!que.empty()){            int i = 0;            while(i < curCount){                p = que.front();                if(p->left != NULL){                    que.push(p->left);                    nextCount++;                }                if(p->right != NULL){                    que.push(p->right);                    nextCount++;                }                que.pop();                i++;                v.push_back(p->val);            }            vec.push_back(v);            v.clear();            curCount = nextCount;            nextCount = 0;        }        return vec;    }};