LeetCode199. Binary Tree Right Side View

Binary Tree Right Side View"/>

LeetCode199. Binary Tree Right Side View

文章目录

• • 一、题目
  • 二、题解

一、题目

Given the root of 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 1:

Input: root = [1,2,3,null,5,null,4]
Output: [1,3,4]
Example 2:

Input: root = [1,null,3]
Output: [1,3]
Example 3:

Input: root = []
Output: []

Constraints:

The number of nodes in the tree is in the range [0, 100].
-100 <= Node.val <= 100

二、题解

类似二叉树的层序遍历，记录每一层中弹出的最后一个数即可

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode() : val(0), left(nullptr), right(nullptr) {}*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}* };*/
class Solution {
public:vector<int> rightSideView(TreeNode* root) {vector<int> res;queue<TreeNode*> q;if(root != nullptr) q.push(root);while(!q.empty()){int size = q.size();while(size--){TreeNode* tmp = q.front();q.pop();if(size == 0) res.push_back(tmp->val);if(tmp->left != nullptr) q.push(tmp->left);if(tmp->right != nullptr) q.push(tmp->right);}}return res;}
};