2264. Largest 3-Same-Digit Number in String
Description
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 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
num
or 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 <= 1000
num
only consists of digits.
Solutions
Solution 1: Enumeration
We can enumerate each digit $i$ from large to small, where $0 \le i \le 9$, and then check whether the string $s$ consisting of three consecutive $i$ is a substring of $num$. If it is, we directly return $s$.
If we have enumerated all the possible values of $i$ and still haven't found a substring that satisfies the condition, we return an empty string.
The time complexity is $O(10 \times n)$, where $n$ is the length of the string $num$. The space complexity is $O(1)$.
1 2 3 4 5 6 |
|
1 2 3 4 5 6 7 8 9 10 11 |
|
1 2 3 4 5 6 7 8 9 10 11 12 |
|
1 2 3 4 5 6 7 8 |
|
1 2 3 4 5 6 7 8 9 |
|