Ways To Tile A Floor

import java.util.*;

class Solution {
    public int numberOfWays(int n) {
        Map<Integer, Integer> hm = new HashMap<>();

        return find(hm, n);
    }

    private int find(Map<Integer, Integer> hm, int n) {
        if (n == 0)
            return 1;
        if (n < 0)
            return 0;
        if (hm.containsKey(n))
            return hm.get(n);

        int ans = find(hm, n - 1) + find(hm, n - 2);
        hm.put(n, ans);

        return ans;
    }
};