English
1461. Check If a String Contains All Binary Codes of Size K 
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 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:
java
public class CheckIfaStringContainsAllBinaryCodesOfSizeK {
public static boolean hasAllCodes(String s, int k) {
int count = 1 << k; // this is same as 2^K
Set<String> res = new HashSet<>();
for (int i = k; i <= s.length(); i++) {
String temp = s.substring(i - k, i);
if (!res.contains(temp)) {
res.add(temp);
count--;
}
if (count == 0)
return true;
}
return false;
}
public static void main(String[] args) {
System.out.println(hasAllCodes("00110", 2));
}
}
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