LeetCode - Binary Tree Right Side View

Binary Tree Right Side View

2015.4.17 06:04

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,

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].

You should return [1, 3, 4].

Solution:

　　Recursion can provide you with a short solution. So make it simple.

Accepted code:

 1 // 1AC, easy with recursive
 2 /**
 3  * Definition for binary tree
 4  * struct TreeNode {
 5  *     int val;
 6  *     TreeNode *left;
 7  *     TreeNode *right;
 8  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 9  * };
10  */
11 class Solution {
12 public:
13     vector<int> rightSideView(TreeNode *root) {
14         vector<int> res;
15         if (root == nullptr) {
16             return res;
17         }
18         
19         dfs(root, 1, res);
20         return res;
21     }
22 private:
23     void dfs(TreeNode *ptr, int dep, vector<int> &res) {
24         if (dep > res.size()) {
25             res.push_back(ptr->val);
26         }
27         
28         if (ptr->right != nullptr) {
29             dfs(ptr->right, dep + 1, res);
30         }
31         if (ptr->left != nullptr) {
32             dfs(ptr->left, dep + 1, res);
33         }
34     }
35 };