leetcode 199. 二叉树的右视图（C++、python）

给定一棵二叉树，想象自己站在它的右侧，按照从顶部到底部的顺序，返回从右侧所能看到的节点值。

示例:

输入: [1,2,3,null,5,null,4]
输出: [1, 3, 4]
解释:

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

C++

/**
 * 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:
    void dfs(TreeNode* root, map<int,int>& tmp, int num)
    {
        if(root)
        {
            tmp[num]=root->val;
            dfs(root->left,tmp,num+1);
            dfs(root->right,tmp,num+1);
        }
    }
    
    vector<int> rightSideView(TreeNode* root) 
    {
        map<int,int> tmp;
        dfs(root,tmp,0);
        vector<int> res;
        for(auto it:tmp)
        {
            res.push_back(it.second);
        }
        return res;
    }
};

python

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def dfs(self,root,dic,num):
        if root:
            dic[num]=root.val
            self.dfs(root.left,dic,num+1)
            self.dfs(root.right,dic,num+1)
    
    def rightSideView(self, root: TreeNode) -> List[int]:
        dic={}
        self.dfs(root,dic,0)
        res=[]
        for key in dic:
            res.append(dic[key])
        return res