Find Longest Special Substring That Occurs Thrice I
Find Longest Special Substring That Occurs Thrice I is a Medium Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Sliding Window pattern, in the Variable Size (Condition-Based) subpattern.
Problem statement
You are given a string s that consists of lowercase English letters.
A string is called special if it is made up of only a single character. For example, the string "abc" is not special, whereas the strings "ddd", "zz", and "f" are special.
Return the length of the longest special substring of s which occurs at least thrice, or -1 if no special substring occurs at least thrice.
A substring is a contiguous non-empty sequence of characters within a string.
Example 1:
Input: s = "aaaa" Output: 2 Explanation: The longest special substring which occurs thrice is "aa": substrings "aaaa", "aaaa", and "aaaa". It can be shown that the maximum length achievable is 2.
Example 2:
Input: s = "abcdef" Output: -1 Explanation: There exists no special substring which occurs at least thrice. Hence return -1.
Example 3:
Input: s = "abcaba" Output: 1 Explanation: The longest special substring which occurs thrice is "a": substrings "abcaba", "abcaba", and "abcaba". It can be shown that the maximum length achievable is 1.
Constraints:
- 3 <= s.length <= 50
- s consists of only lowercase English letters.
Topics and companies
Topics: Hash Table, String, Binary Search, Sliding Window, Counting.
How to practise Find Longest Special Substring That Occurs Thrice I on Thita.ai
Starter code is provided in C, C#, C++, Go, Java, JavaScript and Python. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(26 * 3 + n * 3) time and O(26 * 3) space.
Open Find Longest Special Substring That Occurs Thrice I in the code editor, or read the Find Longest Special Substring That Occurs Thrice I editorial for a worked solution with its approach and complexity analysis.
Where Find Longest Special Substring That Occurs Thrice I sits in the DSA pattern sheet
- Sliding Window pattern guide
- Variable Size (Condition-Based) subpattern
- The full DSA patterns sheet
- All coding practice problems
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