How do you solve Make Three Strings Equal on LeetCode?

Make Three Strings Equal (LeetCode #2937) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: Finding the longest common prefix is crucial to minimizing operations.

What is the brute force solution for Make Three Strings Equal?

The brute force approach for Make Three Strings Equal is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach involves checking all possible ways to delete characters from the strings until they match. This is straightforward but inefficient, as it may require many operations to find a solution. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Make Three Strings Equal?

Make Three Strings Equal uses the following concepts: String. The recommended patterns to study are: Two Pointers, String Matching.

What are the interview tips for Make Three Strings Equal?

Always check for edge cases, such as strings with no common characters. Explain your thought process clearly while coding, as this shows your problem-solving skills. Practice identifying patterns in problems, as many string-related problems can be solved using similar techniques.

What are common mistakes when solving Make Three Strings Equal?

Not considering the case where the strings have no common prefix. Overcomplicating the problem by trying to generate all substrings instead of focusing on prefixes.

#2937

Make Three Strings Equal

Easy

StringTwo PointersString Matching

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

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

💡

Intuition

Time O(n)Space O(1)

The optimal approach focuses on finding the longest common prefix of the three strings. By identifying this prefix, we can directly calculate how many characters need to be deleted from each string to make them equal.

⚙️

Algorithm

3 steps

1Step 1: Find the length of the longest common prefix of the three strings.
2Step 2: Calculate the number of operations needed to delete characters from each string to reach this prefix.
3Step 3: Return the total number of operations.

solution.py12 lines

1# Full working Python code
2
3def min_operations_optimal(s1, s2, s3):
4    min_length = min(len(s1), len(s2), len(s3))
5    common_length = 0
6    while (common_length < min_length and 
7           s1[common_length] == s2[common_length] == s3[common_length]):
8        common_length += 1
9    return (len(s1) - common_length) + (len(s2) - common_length) + (len(s3) - common_length)
10
11# Example usage
12print(min_operations_optimal('abc', 'abb', 'ab'))

ℹ

Complexity note: This complexity is efficient because we only traverse the strings once to find the common prefix, making it linear with respect to the length of the strings.

1Finding the longest common prefix is crucial to minimizing operations.
2If the first characters of the strings differ, they can never be made equal.

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