1461 Check If a String Contains All Binary Codes of Size K

Given a binary string s and an integer k.

Return True if every binary code of length k is a substring of s. Otherwise, return False.

 

Example 1:

Input: s = "00110110", k = 2
Output: true

 public static boolean hasAllCodes(String s, int k) {
        int count  = 0;
        int start = 0;
        HashSet<String> seen = new HashSet<>();

        for (int i=0;i<s.length();i++){
            count++;
            if (count==k){
                seen.add(s.substring(start,k+start));
                count--;
                start++;
            }
        }
        return seen.size()==Math.pow(2,k);;
    }
Explanation: The binary codes of length 2 are "00", "01", "10" and "11". They can be all found as substrings at indicies 0, 1, 3 and 2 respectively.