binaryTreeRightSideView.cpp

/**
 * 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) {
        if(!root)
            return vector<int> ();
            
        vector<int> ans;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()){
            int size = q.size();
            for(int i = 0; i < size; i++){
                auto t = q.front();
                q.pop();
                if(i == size - 1)
                    ans.push_back(t -> val);
                
                if(t -> left)
                    q.push(t -> left);
                
                if(t -> right)
                    q.push(t -> right);
            }
        }
        return ans;
    }
};