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:**

```
class Solution {
public boolean hasAllCodes(String s, int k) {
int need = 1<<k;
Set<String> set=new HashSet<>();
for(int i=k;i<=s.length();i++)
{
String sub = s.substring(i-k,i);
if(!set.contains(sub))
{
set.add(sub);
need--;
if(need==0)
return true;
}
}
return false;
}
}
```

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