Binary Tree Right Side View - Easy BFS

Binary Tree     Breadth-First Search     Depth-First Search     Medium     Tree    

Problem Statement:

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

Solution:

class Solution {
public:
    vector<int> rightSideView(TreeNode* root) 
    {
        if (!root) return {};
        vector<int>res;
        queue<TreeNode *>Q;
        Q.push(root);
        while (!Q.empty())
        {
            int qsize = Q.size();
            for (int i=0; i<qsize; i++)
            {
                root = Q.front();
                Q.pop();
                if (root->left) Q.push(root->left);
                if(root->right) Q.push(root->right);
            }
            res.push_back(root->val);
        }
        return res;
    }
};