What algorithm would you use to establish if two strings could match by swapping one or no characters?

Question Analysis

The question is asking you to determine whether two strings can be made identical by swapping at most one pair of characters in one of the strings. This is a common problem in coding interviews that tests your understanding of string manipulation, character matching, and algorithmic thinking. The problem involves:

• Understanding what it means for two strings to "match" (i.e., become identical).
• Identifying the minimal operation (swapping one pair of characters) that can make them match.
• Considering edge cases, such as identical strings or strings that are fundamentally different.

Answer

To determine if two strings can match by swapping one or no characters, you can follow these steps:

1. Check Length: If the strings have different lengths, it is impossible for them to match with just a single swap.

2. Identify Differences: Traverse both strings simultaneously and note the indices where the characters differ. Store these indices.

3. Analyze Differences:

   • Zero Differences: If there are no differing indices, the strings are already identical, so they trivially match with zero swaps.
   • Two Differences: If there are exactly two differing indices, check if swapping the characters at these indices in one of the strings results in identical strings.
   • More than Two Differences: If there are more than two differing indices, the strings cannot be made identical with a single swap.

4. Conclusion: Based on the above checks, you can conclude if the strings can match by swapping one or no characters.

Here's a potential implementation in Python:

def can_match_with_one_swap(s1, s2):
    # Check if lengths are different
    if len(s1) != len(s2):
        return False
    
    # Find indices where characters differ
    differing_indices = []
    for i in range(len(s1)):
        if s1[i] != s2[i]:
            differing_indices.append(i)
    
    # Analyze the differing indices
    if len(differing_indices) == 0:
        return True  # Strings are already identical
    elif len(differing_indices) == 2:
        # Check if swapping the differing characters makes the strings identical
        i, j = differing_indices
        return s1[i] == s2[j] and s1[j] == s2[i]
    else:
        return False  # More than two differences

# Example usage:
# print(can_match_with_one_swap("converse", "conserve"))  # Should return True
# print(can_match_with_one_swap("converse", "converso"))  # Should return False

This solution efficiently checks the conditions for the strings to match with one swap, ensuring clarity and correctness in the approach.