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
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:

• Set
• << left shift by k bits

1
2
3
4
5
6
7
8
9
10
11

class Solution:
    def hasAllCodes(self, s: str, k: int) -> bool:
        count = 1 << k
        seen = set()
        for i in range(len(s) - k, -1, -1):
            num = s[i:i+k]
            if num not in seen:
                seen.add(num)
                count -= 1
            if not count: return True
            if i < count: return False

references

• https://leetcode.com/problems/check-if-a-string-contains-all-binary-codes-of-size-k/