💡 Problem Formulation: Consider two strings, for instance, ‘converse’ and ‘conserve’. We want to devise a way to determine if one string can be transformed into the other by swapping characters. The objective is to see if, through a series of character exchanges within the strings, both can become identical. For example, swapping ‘v’ with ‘s’ in ‘converse’ would result in ‘conserve’, making them equal.
Method 1: Frequency Counter
This method employs a dictionary to count the frequency of each character in both strings. If both strings have the same character frequency, they can be made equal by swapping characters.
Here’s an example:
from collections import Counter
def can_be_equal_by_swapping(str1, str2):
return Counter(str1) == Counter(str2)
print(can_be_equal_by_swapping('converse', 'conserve'))
Output:
True
This code snippet creates two Counter objects from the collections module, which are essentially dictionaries that map characters to the number of times they appear in the strings. By comparing these Counters, we can ascertain if the strings can be made equal through swaps.
Method 2: Sorting Both Strings
If two strings can be made equal by swapping characters, then sorting both strings should result in identical strings. This method sorts the strings and then compares them for equality.
Here’s an example:
def can_be_equal_by_swapping(str1, str2):
return sorted(str1) == sorted(str2)
print(can_be_equal_by_swapping('converse', 'conserve'))
Output:
True
Sorting the strings alphabetically rearranges the characters so that if both strings have identical sets of characters, they will match when compared directly after sorting.
Method 3: Using Set and Length Check
This method checks if the set of characters in both strings is the same and that the strings are of the same length. Due to the possibility of duplicate characters, this method is not always accurate on its own but can quickly rule out strings that definitely cannot be made equal.
Here’s an example:
def can_be_equal_by_swapping(str1, str2):
return set(str1) == set(str2) and len(str1) == len(str2)
print(can_be_equal_by_swapping('converse', 'conserve'))
Output:
True
This code performs a fast initial check by comparing the unique sets of characters and the length of the strings. However, it doesn’t account for the frequency of characters, which could lead to false positives if unchecked.
Method 4: Custom Character Count Comparison
This method manually tallies the occurrences of each character in both strings and compares their counts without using additional data structures like the Counter.
Here’s an example:
def can_be_equal_by_swapping(str1, str2):
if len(str1) != len(str2):
return False
for char in set(str1):
if str1.count(char) != str2.count(char):
return False
return True
print(can_be_equal_by_swapping('converse', 'conserve'))
Output:
True
The code snippet above iterates over the set of unique characters in the first string and checks if both strings have the same number of occurrences for each character. While it avoids external libraries, it can be inefficient for strings with many repeating characters due to multiple passes for each unique character.
Bonus One-Liner Method 5: Using Python’s All()
This concise one-liner uses Python’s powerful all() function to achieve the same result, combining the set and count checks into a single condition inside a generator expression.
Here’s an example:
def can_be_equal_by_swapping(str1, str2):
return len(str1) == len(str2) and all(str1.count(c) == str2.count(c) for c in set(str1))
print(can_be_equal_by_swapping('converse', 'conserve'))
Output:
True
This one-liner version compactly checks for equal length of strings and the same number of occurrences for each character present in the first string. It’s efficient in terms of writing less code but suffers from the same efficiency issues as Method 4 for large input sizes.
Summary/Discussion
- Method 1: Frequency Counter. Utilizes the Counter class to provide a simple and effective solution. Strengths: concise and clear. Weaknesses: potentially inefficient with large strings.
- Method 2: Sorting Both Strings. Another simple approach by using sorting. Strengths: easy to understand and works well for small datasets. Weaknesses: sorting can be slow for large strings.
- Method 3: Using Set and Length Check. Provides quick preliminary check. Strengths: very fast for non-equal length strings or different sets of characters. Weaknesses: does not consider character frequency.
- Method 4: Custom Character Count Comparison. Does not depend on additional libraries and provides a manual solution. Strengths: straightforward logic. Weaknesses: inefficient with multiple calls to count for duplicates.
- Method 5: One-Liner Using All(). A concise statement that checks for necessary conditions. Strengths: compact code. Weaknesses: can be slow due to repeated counting of characters.