#2839

Easy

auto_awesomeString-driven solution strategy

LeetCode Problem Workspace

Check if Strings Can be Made Equal With Operations I

Determine if two strings can be made equal by repeatedly swapping characters at any two indices in each string.

Problem Statement

You are given two strings, s1 and s2, both consisting of lowercase English letters and having a length of 4. You can perform the operation of swapping characters at any two indices of either string any number of times.

Your task is to determine if it is possible to make both strings equal using the above operation, returning true if they can be made equal, and false otherwise.

Examples

Example 1

Input: s1 = "abcd", s2 = "cdab"

Output: true

We can do the following operations on s1:

Choose the indices i = 0, j = 2. The resulting string is s1 = "cbad".
Choose the indices i = 1, j = 3. The resulting string is s1 = "cdab" = s2.

Example 2

Input: s1 = "abcd", s2 = "dacb"

Output: false

It is not possible to make the two strings equal.

Constraints

s1.length == s2.length == 4
s1 and s2 consist only of lowercase English letters.

Solution Approach

Brute Force Approach

Since the strings are very small, a brute-force approach can be effective. Iterate through all possible pairs of indices, swap them in one of the strings, and check if the strings become equal.

Optimization with String Matching

A more efficient approach would be to first check if the strings contain the same set of characters. If they do, you can try to directly match the strings by swapping indices until they match.

Pattern-based Matching

If the two strings can be rearranged to match each other through index swapping, their character sequences should be rotations of one another. Verify if one string is a rotation of the other.

Complexity Analysis

Metric	Value
Time	Depends on the final approach
Space	Depends on the final approach

The time and space complexity depend on the approach used. The brute force solution might involve checking multiple combinations of swaps, leading to a higher time complexity. Optimizing by checking rotations or matching patterns will reduce the complexity significantly.

What Interviewers Usually Probe

Candidate understands the string-driven solution approach.
Candidate suggests efficient ways to handle small input sizes.
Candidate proposes checking string rotations or character set equivalence as a strategy.

Common Pitfalls or Variants

Common pitfalls

Overcomplicating the problem by using unnecessary algorithms or data structures.
Failing to consider small input sizes which allow for brute-force solutions.
Not checking for rotations or permutations of strings which could offer a simpler solution.

Follow-up variants

If strings are of larger length, brute force would not be feasible, and more efficient algorithms are required.
A variant might include using recursion to repeatedly swap characters until a solution is found.
Testing performance with larger strings as input can provide insight into optimal solution techniques.

FAQ

What is the main approach for solving the 'Check if Strings Can be Made Equal With Operations I' problem?

The main approach involves checking if one string is a rotation or permutation of the other, and performing swaps between indices to make the strings equal.

How can I optimize the brute force approach for this problem?

Optimization can be achieved by recognizing patterns such as string rotations or matching the character sets of both strings before attempting swaps.

Can I use a recursive approach to solve this problem?

Yes, you could use recursion to attempt all possible swaps and check if the strings become equal.

Are there any performance concerns with brute-forcing this problem?

Since the strings are small (length 4), brute force is manageable. However, for larger strings, brute force would be inefficient, and optimized methods should be used.

What are the most common mistakes when solving the 'Check if Strings Can be Made Equal With Operations I' problem?

The most common mistakes include overcomplicating the solution, not leveraging the small input size for brute-force, and not considering string rotations or permutations.

terminal

Solution

Solution 1: Counting

We observe the operation in the problem, and find that if the parity of the two indices $i$ and $j$ of the string is the same, then their order can be changed by swapping.

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class Solution:
    def canBeEqual(self, s1: str, s2: str) -> bool:
        return Counter(s1[::2]) == Counter(s2[::2]) and Counter(s1[1::2]) == Counter(
            s2[1::2]
        )

Continue Practicing

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