Python - Pairs with Sum equal to K in tuple list

Sometimes, while working with data, we can have a problem in which we need to find the sum of pairs of tuple list. And specifically the sum that is equal to K. This kind of problem can be important in web development and competitive programming. Lets discuss certain ways in which this task can be performed. 

Method #1: Using loop This can be solved using loop. This is brute way in which this task is performed. In this, we iterate the list for pair summation and retain whose sum is K. 

The original list is : [(4, 5), (6, 7), (3, 6), (1, 2), (1, 8)]
List after extracting pairs equal to K : [(4, 5), (3, 6), (1, 8)]

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 list comprehension This is yet another way in which this task can be performed. In this, we extract the elements in similar method as above, the difference is that we perform this task as shorthand and in one line. 

The original list is : [(4, 5), (6, 7), (3, 6), (1, 2), (1, 8)]
List after extracting pairs equal to K : [(4, 5), (3, 6), (1, 8)]

Time Complexity: O(n), where n is the length of the list test_list 
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the res list 

Method #3 : Using sum() and list() methods

The original list is : [(4, 5), (6, 7), (3, 6), (1, 2), (1, 8)]
List after extracting pairs equal to K : [(4, 5), (3, 6), (1, 8)]

Method #4 : Using lamda and filter() methods

The original list is : [(4, 5), (6, 7), (3, 6), (1, 2), (1, 8)]
List after extracting pairs equal to K : [(4, 5), (3, 6), (1, 8)]

Time complexity: O(n)

Auxiliary Space: O(n)

Method 5 : Using a dictionary. 

step-by-step approach:

Initialize an empty dictionary dict_pairs.
Loop through each tuple t in the input list test_list.
Calculate the difference diff between the target sum K and the first element of the tuple t[0].
If diff is already a key in the dictionary, append the current tuple t to the list of tuples mapped to that key.
If diff is not already a key in the dictionary, add it as a key with a value of a list containing the current tuple t.
Return the values of the dictionary as the final result.

The original list is : [(4, 5), (6, 7), (3, 6), (1, 2), (1, 8)]
List after extracting pairs equal to K : [(4, 5), (3, 6), (1, 8)]

Time complexity: O(n), where n is the number of tuples in the input list.
Auxiliary space: O(n), to store the dictionary of pairs.