LeetCode.102 Binary Tree Level Order Traversal

102. 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,null,null,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) {} * }; */vector< vector<int> > levelOrder(TreeNode* root){vector<TreeNode*> node(1, root), node_temp;vector<int> temp;vector< vector<int> > result;while(!node.empty() && node[0] != NULL){node_temp.clear();temp.clear();for(int i = 0; i < node.size(); i++){temp.push_back(node[i]->val);if(node[i]->left != NULL){node_temp.push_back(node[i]->left);}if(node[i]->right != NULL){node_temp.push_back(node[i]->right);}}result.push_back(temp);node = node_temp;}return result;}