Python | Find all distinct pairs with difference equal to k

Given a list of integers and a positive integer k, write a Python program to count all distinct pairs with difference equal to k.

Examples:

Input : [1, 5, 3, 4, 2], k = 3
Output : [(5, 2), (4, 1)]

Input : [8, 12, 16, 4, 0, 20], k = 4
Output : [(8, 4), (12, 8), (16, 12), (4, 0), (20, 16)]

Approach #1 : Python list comprehension

We will use list comprehension using two loops using ‘e1’ and ‘e2’ that will traverse given list. We check if e1-e2 == k or not and return the (e1, e2) tuple respectively. Finally, a list with required tuples will be returned.

 # Python3 program to Find all distinct  # pairs with difference equal to k    def findPairs(lst, k):            return [(e1, e2) for e1 in lst              for e2 in lst if (e1-e2 == k)]            # Driver code lst = [1, 5, 3, 4, 2] k = 3 print(findPairs(lst, k))

Output:

[(5, 2), (4, 1)]

Approach #2 :

This is an efficient approach with respect to the above approach as it uses only O(n) space. We take an empty list to store the output. Then, we use a loop with iterator ‘e’ to traverse through given list. In every iteration, we check is e+k i.e the required pair integer for e is available or not. If yes, we append the tuple to ‘res’.

 # Python3 program to Find all distinct  # pairs with difference equal to k    def findPairs(lst, k):     res = []     for e in lst:         if e + k in lst:             res.append(tuple((e, e + k)))                    return res        # Driver code lst = [1, 5, 3, 4, 2] k = 3 print(findPairs(lst, k))

Output:

[(1, 4), (2, 5)]

Approach #3 : combinations() from itertools module

The best approach is to use the inbuilt function from itertools module. combinations() produces an iterator over tuples of all combinations of n elements in inputs. We make the use of these combinations and ouptut those having ‘k’ difference.

 # Python3 program to Find all distinct  # pairs with difference equal to k from itertools import combinations    def findPairs(lst, k):     return [(x, y) for x, y in combinations(lst, r = 2)                    if abs(x - y) == k]                # Driver code lst = [1, 5, 3, 4, 2] k = 3 print(findPairs(lst, k))

Output:

[(1, 4), (5, 2)]

My Personal Notes arrow_drop_up If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.