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Check If a String Contains All Binary Codes of Size K

Updated: Mar 24, 2021

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
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.

Example 2:

Input: s = "00110", k = 2
Output: true

Example 3:

Input: s = "0110", k = 1
Output: true
Explanation: The binary codes of length 1 are "0" and "1", it is clear that both exist as a substring. 

Example 4:

Input: s = "0110", k = 2
Output: false
Explanation: The binary code "00" is of length 2 and doesn't exist in the array.

Example 5:

Input: s = "0000000001011100", k = 4
Output: false

Constraints:

  • 1 <= s.length <= 5 * 10^5

  • s consists of 0's and 1's only.

  • 1 <= k <= 20

Solution:


class Solution {
    public boolean hasAllCodes(String s, int k) {
        int need = 1<<k;
        Set<String> set=new HashSet<>();
        
        for(int i=k;i<=s.length();i++)
        {
            String sub = s.substring(i-k,i);
            if(!set.contains(sub))
            {
                set.add(sub);
                need--;
                if(need==0)
                    return true;
            }
        }
       return false; 
    }
}


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