Binary_Tree_Right_Side_View.cpp

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

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

Input: root = []
Output: []

SOLUTION :-
  
  /**
 * 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> ans;
        if(root==NULL)
            return ans;
        
        queue<TreeNode *> q;
        q.push(root);
        while(q.empty()==false)
        {
            int cnt = q.size();
            for(int i=0;i<cnt;i++)
            {
                TreeNode *curr = q.front();
                q.pop();
                
                if(i == cnt-1)
                    ans.push_back(curr->val);
                if(curr->left)
                    q.push(curr->left);
                if(curr->right)
                    q.push(curr->right);
            }
        }
        
        return ans;
    }
};