Python – Remove similar index elements in Strings

Given two strings, removed all elements from both, which are the same at similar index.

Input : test_str1 = ‘geels’, test_str2 = ‘beaks’ 
Output : gel, bak 
Explanation : e and s are removed as occur in same indices. 

Input : test_str1 = ‘neveropen’, test_str2 = ‘neveropen’ 
Output : ”, ” 
Explanation : Same strings, all same index, hence removed.

Method #1 : Using loop + zip() + join()

In this, we pair elements with its index using join(), and check for inequality to filter only dissimilar elements in both strings, join() is used to convert result in strings.

The original string 1 is : neveropen
The original string 2 is : beaks
Modified String 1 : ge
Modified String 2 : ba

Method #2: Using list comprehension

Performs task using similar method as above, just one-liner to perform task in compact form.

The original string 1 is : neveropen
The original string 2 is : beaks
Modified String 1 : ge
Modified String 2 : ba

Time Complexity: O(n)
Auxiliary Space: O(n)

Method #3:  Using index() and replace() methods

The original string 1 is : neveropen
The original string 2 is : beaks
Modified String 1 : ge
Modified String 2 : ba

Method #4: Using enumerate() function

Step-by-step approach:

1. Initialize the two given strings.
2. Iterate through the characters of the strings using enumerate() and list comprehension.
3. For each character, compare it with the character at the corresponding index in the other string.
4. If they are not equal, add the character to a list.
5. Join the characters in the list to form the modified strings.
6. Print the modified strings.

Below is the implementation of the above approach:

The original string 1 is : neveropen
The original string 2 is : beaks
Modified String 1 : ge
Modified String 2 : ba

Time Complexity: O(n), where n is the length of the strings.
Auxiliary Space: O(n), where n is the length of the strings.

Method #5: Using map() + lambda function + zip() + join()

Step-by-step approach:

• Initialize two strings test_str1 and test_str2 
• Create two lists list1 and list2 by using the map() function to apply a lambda function
• Zip the two lists list1 and list2 together using zip() to get a list of tuples
• Use another map() function to apply a lambda function to each tuple in the zipped list
• Join the resulting list of characters from the previous step using the join() function to get the modified strings.
• Print the modified strings.

Below is the implementation of the above approach:

The original string 1 is : neveropen
The original string 2 is : beaks
Modified String 1 : ge
Modified String 2 : ba

The time complexity of this approach is O(n), where n is the length of the input strings.
The auxiliary space is also O(n), since we create a new string of length n to store the result.

Method 6:  use the built-in filter() function. 

Step-by-step approach:

• Initialize an empty string to store the result.
• Use the filter() function to create a filter object that only keeps characters that are not similar in index in both strings.
• Use the join() function to convert the filtered object into a string.

Below is the implementation of the above approach:

The original string 1 is : neveropen
The original string 2 is : beaks
Modified String 1 : ge
Modified String 2 : ba

Time complexity: O(n), where n is the length of the strings.
Auxiliary space: O(n), where n is the length of the strings, because we create a temporary list to store the filtered elements before joining them into a string.