Python – Segregate elements by delimiter

Given a list of Strings, segregate each string by delimiter and output different lists for prefixes and suffixes.

Input: test_list = [“7$2”, “8$5”, “9$1”], delim = “$” 
Output : [‘7’, ‘8’, ‘9’], [‘2’, ‘5’, ‘1’] 
Explanation  Different lists for prefixes and suffixes of “$” 

Input  test_list = [“7*2”, “8*5”, “9*1”], delim = “*” 
Output : [‘7’, ‘8’, ‘9’], [‘2’, ‘5’, ‘1’] 
Explanation: Different lists for prefixes and suffixes of “*”

Method #1 : Using list comprehension + split()

This is one of the ways in which this task can be performed. In this, we perform segregation using split(), the first part of the split is compiled to one list comprehension and next to the other.

The original list : ['7$2', '8$5', '9$1', '8$10', '32$6']
The filtered list 1 : ['7', '8', '9', '8', '32']
The filtered list 2 : ['2', '5', '1', '10', '6']

Time Complexity: O(n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(n), where n is the number of elements in the list “test_list”.

Method #2 : Using map() + list + zip() + generator expression

The combination of above functions can be used to solve this problem. In this, we extend the list construction logic using map() and zip() is used to perform split() functionality to each element.

The original list : ['7$2', '8$5', '9$1', '8$10', '32$6']
The filtered list 1 : ['7', '8', '9', '8', '32']
The filtered list 2 : ['2', '5', '1', '10', '6']

Time Complexity: O(n²)
Auxiliary Space: O(n)

Method #3 : Using index() method and slicing

The original list : ['7$2', '8$5', '9$1', '8$10', '32$6']
The filtered list 1 : ['7', '8', '9', '8', '32']
The filtered list 2 : ['2', '5', '1', '10', '6']

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

Method #4: Using slicing

The original list : ['7$2', '8$5', '9$1', '8$10', '32$6']
The filtered list 1 : ['7', '8', '9', '8', '32']
The filtered list 2 : ['2', '5', '1', '10', '6']

Time complexity: O(n), where n is the number of elements in the test_list.
Auxiliary space: O(n), where n is the number of elements in the test_list.

Method #5: Using a dictionary and a loop

This code first creates an empty dictionary res_dict. It then loops through each element of the list, splits it by the delimiter, and stores the key and value in the dictionary. If the key is not already in the dictionary, it creates a new empty list for that key. Then it appends the key to the res1 list, and extends the res2 list with the values for that key.

The filtered list 1 : ['9', '8', '7', '32']
The filtered list 2 : ['1', '5', '10', '2', '6']

Time complexity: O(n), where n is the length of the input list.
Auxiliary space: O(n), where n is the length of the input list.

Method #6: Using a defaultdict

Step-by-step approach:

• Import defaultdict from the collections module
• Define the test_list and the delimiter as before
• Initialize a defaultdict with the list constructor. This will create a dictionary with default values as empty lists.
• Loop through the test_list, splitting each element using the delimiter, and appending the value to the dictionary corresponding to the key.
• Convert the keys of the dictionary to a list for the first filtered list (res1).
• For the second filtered list (res2), use a nested list comprehension to extract all the values from the dictionary and flatten them into a single list.
• Print the results 

The filtered list 1 : ['7', '8', '9', '32']
The filtered list 2 : ['2', '5', '10', '1', '6']

Time complexity: O(n)
Auxiliary space: O(n) (for the dictionary)