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

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

 

Solutions

Solution: Bit Manipulation

• Time complexity: O(n)
• Space complexity: O(2^k)

 

JavaScript

/**
 * @param {string} s
 * @param {number} k
 * @return {boolean}
 */
const hasAllCodes = function (s, k) {
  const n = s.length;
  const codes = new Set();
  const MAX_CODE = 1 << k;
  let current = 0;

  for (let index = 0; index < n; index++) {
    current <<= 1;
    current |= Number(s[index]);

    if (index < k - 1) continue;

    current &= MAX_CODE - 1;
    codes.add(current);

    if (codes.size === MAX_CODE) return true;
  }

  return false;
};