Today, we will solve the 12 th problem of the March LeetCoding Challenge.

Problem Statement

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

Solution

In this problem, we are asked to find whether we have all the binary codes of size k in a given string.

We know that for a given size k, we can have a total of 2^k numbers. We need to check whether all of those 2^k numbers are present in the given string. For that, we can use a HashSet , to store all the values which we have found out. In the end, we can compare the size of HashSet and 2^k , if they are equal then return true else return false.

The code is given below.

Time Complexity: O(n)

Space Complexity: O(n)

The code can be found here

Check out my other posts on March LeetCoding Challenge 2021.

1. March LeetCoding Challenge — Day 1 — Distribute Candies

2. March LeetCoding Challenge — Day 2 — Set Mismatch

3. March LeetCoding Challenge — Day 3 — Missing Number

4. March LeetCoding Challenge — Day 4 — Intersection of Two Linked Lists

5. March LeetCoding Challenge — Day 5 — Average of Levels in Binary Tree

6. March LeetCoding Challenge — Day 6 — Short Encoding of Words

7. March LeetCoding Challenge — Day 8 — Remove Palindromic Subsequences

8. March LeetCoding Challenge — Day 10 — Integer to Roman