Skip to content

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

Difficulty Topics

Description

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 indices 0, 1, 3 and 2 respectively.

Example 2:

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 3:

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

 

Constraints:

  • 1 <= s.length <= 5 * 105
  • s[i] is either '0' or '1'.
  • 1 <= k <= 20

Solution

check-if-a-string-contains-all-binary-codes-of-size-k.py
class Solution:
    def hasAllCodes(self, s: str, k: int) -> bool:
        n = len(s)
        seen = [False] * (1 << k)
        mask = 0

        for i, x in enumerate(s):
            if i < k:
                if x == "1":
                    mask |= (1 << i)
            else:
                mask >>= 1
                if x == "1":
                    mask |= (1 << (k - 1))

            if i >= k - 1:
                seen[mask] = True

        return all(seen[mask] for mask in range(1 << k))