## DEV Community

Abhishek Chaudhary

Posted on

# Largest 3-Same-Digit Number in String

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 `num` with length `3`.
• 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 `num` or a good integer.

Example 1:

Input: num = "6*777133339"
**Output:
* "777"
Explanation: There are two distinct good integers: "777" and "333".
"777" is the largest, so we return "777".

Example 2:

Input: num = "23*00019"
**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 <= 1000`
• `num` only consists of digits.

SOLUTION:

``````class Solution:
def largestGoodInteger(self, num: str) -> str:
n = len(num)
i = 0
mnum = float('-inf')
while i < n:
ctr = 1
while i < n - 1 and num[i] == num[i + 1]:
i += 1
ctr += 1
i += 1
if ctr >= 3:
mnum = max(mnum, int(num[i - 1]))
if mnum == float('-inf'):
return ""
return str(mnum) * 3
``````