[Leetcode] Binary Tree Right Side View

Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.

For example:
Given the following binary tree,

   1            <--- /   \2     3         <--- \     \  5     4       <---

You should return [1, 3, 4].

/** * 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:    /*algorithm: level order,         level order, book last element     */    vector<int> rightSideView(TreeNode* root) {                vector<int>path;                if(!root)return path;                queue<TreeNode*>L;                L.push(root);                while(!L.empty()){                    int size = L.size();                    TreeNode* t = NULL;                    for(int i = 0;i < size;i++){                        t = L.front();L.pop();                        if(t->left)L.push(t->left);                        if(t->right)L.push(t->right);                    }                    path.push_back(t->val);                }                return path;    }};