LC 199. Binary Tree Right Side View

https://leetcode.com/problems/binary-tree-right-side-view/description/?envType=study-plan-v2&envId=top-interview-150

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

Time Complexity: O(n)
Space: O(n)