題目內容

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.

For example:
Given the following binary tree,

1 <—
/ \
2 3 <—
\ \
5 4 <—

You should return [1, 3, 4].

Credits:
Special thanks to @amrsaqr for adding this problem and creating all test cases.
題目原文

題目簡述

從上到下寫出二叉樹每層最右側節點對應的數值

題目分析

按層次遞迴，並將層數作為遞迴變數使每層只記錄一個數值，從右至左遍歷則使每層右邊節點最先遍歷，該節點數值即可在本層唯一記錄。

程式碼示例

/**
 * 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 recursion(vector<int> &res,TreeNode *root,int level)
    {
        if(root==NULL) return;
        if(res.size()<level) res.push_back(root->val);
        recursion(res,root->right,level+1);
        recursion(res,root->left,level+1);
    }
    vector
 
<int> rightSideView(TreeNode *root)
    {
        vector<int> res;
        recursion(res,root,1);
        return res;
    }
};