Check If a String Contains All Binary Codes of Size K LeetCode solution in Java

1
class Solution {
2
  public boolean hasAllCodes(String s, int k) {
3
    HashSet<String> hs = new HashSet();
4
    for (int i = 0; i <= s.length() - k; i++) {
5
      hs.add(s.substring(i, i + k));
6
    }
7
    if (hs.size() == Math.pow(2, k)) return true;
8
    return false;
9
  }
10
}