LeetCode 199. 二叉树的右视图

class Solution {
public:
    Solution() { res = {}; max_floor = -1; }
    vector<int> res;
    int max_floor;
    void DFS(TreeNode* root, int now_floor) {
        if (root != NULL) {
            if (++now_floor > max_floor) {
                max_floor = now_floor;
                res.push_back(root->val);
            }
            DFS(root->right, now_floor);
            DFS(root->left, now_floor);
        }
    }
    vector<int> rightSideView(TreeNode* root) {
        DFS(root, -1);
        return res;
    }
};