[leetcode] Binary Tree Level Order Traversal

From : https://leetcode.com/problems/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]]

/** * 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>> vct;        if(!root) return vct;vector<TreeNode> box;        box.push_back(*root);        int num1 = 1, num2=0;        while(num1) {            vector<int> curVct;while(num1) {TreeNode node = box.front();curVct.push_back(node.val);box.erase(box.begin());num1--;if(node.left) {box.push_back(*node.left); num2++;}if(node.right){box.push_back(*node.right);num2++;}            }vct.push_back(curVct);num1=num2;num2=0;        }return vct;    }};