You are given a string num representing a large integer. An integer is good if it meets the following conditions:
- It is a substring of
numwith length3. - It consists of only one unique digit.
Return the maximum good integer as a string or an empty string "" if no such integer exists.
Note:
- A substring is a contiguous sequence of characters within a string.
- There may be leading zeroes in
numor a good integer.
Example 1:
Input: num = "6777133339" Output: "777" Explanation: There are two distinct good integers: "777" and "333". "777" is the largest, so we return "777".
Example 2:
Input: num = "2300019" Output: "000" Explanation: "000" is the only good integer.
Example 3:
Input: num = "42352338" Output: "" Explanation: No substring of length 3 consists of only one unique digit. Therefore, there are no good integers.
Constraints:
3 <= num.length <= 1000numonly consists of digits.