How do you solve Repeated Substring Pattern on LeetCode?

Repeated Substring Pattern (LeetCode #459) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: The problem can often be reduced to checking for patterns in strings, which is a common theme in string manipulation problems.

What is the brute force solution for Repeated Substring Pattern?

The brute force approach for Repeated Substring Pattern is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach checks every possible substring of the input string to see if repeating that substring can recreate the original string. This method is straightforward but inefficient for larger strings. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Repeated Substring Pattern?

Repeated Substring Pattern uses the following concepts: String, String Matching. The recommended patterns to study are: String Matching, Pattern Recognition.

What are the interview tips for Repeated Substring Pattern?

Always start with the brute-force solution to demonstrate your understanding of the problem. Discuss the time and space complexity of your solutions clearly. Be prepared to explain your thought process and any trade-offs between different approaches.

What are common mistakes when solving Repeated Substring Pattern?

Not considering edge cases, such as very short strings or strings with no repeating patterns. Overcomplicating the problem by trying to implement complex algorithms when simpler ones exist.

#459

Repeated Substring Pattern

Easy

StringString MatchingString MatchingPattern Recognition

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

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Intuition

Time O(n)Space O(n)

The optimal solution leverages the properties of string concatenation. By concatenating the string with itself and removing the first and last characters, we can check if the original string appears in this new string, which indicates a repeated pattern.

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Algorithm

3 steps

1Step 1: Concatenate the string with itself to form a new string.
2Step 2: Remove the first and last characters of this new string.
3Step 3: Check if the original string exists in this modified string. If it does, return true; otherwise, return false.

solution.py3 lines

1def repeatedSubstringPattern(s):
2    ss = s + s
3    return s in ss[1:-1]

ℹ

Complexity note: The time complexity is O(n) because we are creating a new string that is twice the length of the original. Checking for the substring takes linear time as well.

1The problem can often be reduced to checking for patterns in strings, which is a common theme in string manipulation problems.
2Understanding how string concatenation and substring searching works can lead to efficient solutions.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.