LeetCode [199] 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.

Example:

Input: [1,2,3,null,5,null,4]
Output: [1, 3, 4]
Explanation:

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

/** * 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 { vector<int> ret; public: vector<int> rightSideView(TreeNode* root) { dfs(root, 0); return ret; } void dfs(TreeNode* node, int level){ if(!node) return; if(ret.size()<level+1) ret.push_back(node->val); ret[level] = node->val; dfs(node->left, level+1); dfs(node->right, level+1); } };