5 Best Ways to Check if Single-Element Modification Can Make Arrays Equal in Python

💡 Problem Formulation: Python developers often face the task of determining whether two arrays can be made equal by modifying just one element. Imagine you have two arrays: [1, 2, 3] and [1, 2, 4]. The goal is to assess the possibility of making these arrays identical by altering a maximum of one element in either array. In this context, equal means having the same elements in the same order.

Method 1: Using a Simple Iterative Approach

This method involves iterating through both arrays and comparing elements at the same index positions. If differences are found, we keep track of them. If more than one difference is found, we conclude that the arrays cannot be made equal by modifying just a single element.

Here’s an example:

def can_make_equal_by_one_modification(arr1, arr2):
    differences = 0
    for a, b in zip(arr1, arr2):
        if a != b:
            differences += 1
            if differences > 1:
                return False
    return True if differences == 1 else False

# Example arrays
print(can_make_equal_by_one_modification([1, 2, 3], [1, 2, 4]))

Output: True

This code defines a function that iterates through both provided arrays simultaneously, counting any differences between elements. If the difference count exceeds one, the function returns False. Otherwise, it returns True if exactly one element can be modified to make the arrays equal, or False otherwise.

Method 2: Utilizing the Python Counter

The Counter class from the collections module can be used to compare the frequency of each element in the arrays. If the difference in counts of all elements can be accounted for by a single modification, then the arrays can be made equal.

Here’s an example:

from collections import Counter

def can_make_equal_by_one_modification(arr1, arr2):
    counter_diff = Counter(arr1) - Counter(arr2)
    total_difference = sum(counter_diff.values())
    return total_difference <= 1

# Example arrays
print(can_make_equal_by_one_modification([1, 2, 5], [1, 2, 4]))

Output: True

In this snippet, we use Counter to tally elements from each array and subtract these tallies. We sum up the absolute differences to find out if it’s possible to equalize the arrays by one modification. The function returns True if the total difference is less than or equal to one.

Method 3: Set Difference and Length Check

By converting arrays to sets we can quickly evaluate if the difference between two arrays consists of exactly two elements, which would indicate that modifying one element in any of the arrays could make them equal.

Here’s an example:

def can_make_equal_by_one_modification(arr1, arr2):
    set_diff = set(arr1).symmetric_difference(set(arr2))
    return len(set_diff) == 2

# Example arrays
print(can_make_equal_by_one_modification([1, 2, 3], [1, 2, 4]))

Output: True

This code snippet employs symmetric difference for sets which yields elements unique to each set. If the length of the resultant set is exactly two, one can infer that modifying one element from either array will equate them.

Method 4: Using the Zip Function and List Comprehension

This method combines the zip function with a list comprehension to create a list of booleans for each pair of elements. If there is exactly one False value, it means that changing one element in either array could make them equal.

Here’s an example:

def can_make_equal_by_one_modification(arr1, arr2):
    differences = [a != b for a, b in zip(arr1, arr2)]
    return differences.count(False) == len(arr1)-1

# Example arrays
print(can_make_equal_by_one_modification([1, 2, 3], [1, 2, 4]))

Output: True

In this snippet, the zip function is used to pair elements of the two arrays, while list comprehension checks for inequality. By counting the number of False values and comparing it to the array length minus one, we can verify the possibility of equalizing the arrays with a single modification.

Bonus One-Liner Method 5: Employing a Functional Approach

Employing the built-in ‘filter’ function and lambda expressions, we can filter out non-identical element pairs between the two arrays. If the size of the filtered result is one, then the arrays can be made equal with one modification.

Here’s an example:

can_make_equal_by_one_modification = lambda arr1, arr2: len(list(filter(lambda x: x[0] != x[1], zip(arr1, arr2)))) == 1

# Example arrays
print(can_make_equal_by_one_modification([1, 2, 3], [1, 3, 4]))

Output: False

This compact method leverages a lambda function to check if there is exactly one pair of different elements between the two arrays by comparing their zipped tuples. A single difference implies the arrays can be equalized through one change.

Summary/Discussion

• Method 1: Iterative Comparison. Strengths: Simple and easy to understand. Weaknesses: Potentially slow for long arrays.
• Method 2: Counter Difference. Strengths: Utilizes Python’s built-in structures for efficient computation. Weaknesses: Might not be as intuitive as other methods.
• Method 3: Set Difference and Length Check. Strengths: Fast for arrays with a large number of unique elements. Weaknesses: Fails if arrays have duplicate values that need to be accounted for.
• Method 4: Zip and List Comprehension. Strengths: Pythonic and concise. Weaknesses: Slightly complex logic with list comprehension.
• Bonus Method 5: Functional One-Liner. Strengths: Very concise. Weaknesses: Might be cryptic and challenging for beginners to understand.