Python – Find Minimum Pair Sum in list

Sometimes, we need to find the specific problem of getting the pair which yields the minimum sum, this can be computed by getting initial two elements after sorting. But in some case, we don’t with to change the ordering of list and perform some operation in the similar list without using extra space. Let’s discuss certain ways in which this can be performed.

Method #1 : Using list comprehension + min() + combination() + lambda
This particular task can be performed using the combination of above functions in which we use list comprehension to bind all the functionalities and min function to get the minimum sum, combination function finds all sums internally and lambda function is used to compute the sum.

# Python3 code to demonstrate
# Minimum Pair Sum
# using list comprehension + min() + combinations() + lambda
from itertools import combinations

# initializing list
test_list = [3, 4, 1, 7, 9, 1]

# printing original list
print("The original list : " + str(test_list))

# using list comprehension + min() + combinations() + lambda
# Minimum Pair Sum
res = min(combinations(test_list, 2), key = lambda sub: abs(sub[0]-sub[1]))

# print result
print("The minimum sum pair is : " + str(res))

Output :

The original list : [3, 4, 1, 7, 9, 1]
The minimum sum pair is : (1, 1)

Method #2 : Using list comprehension + nsmallest() + combination() + lambda
This method has potential of not only finding a single minimum but also k minimum sum pairs if required and uses nsmallest function instead of min function to achieve this functionality.

# Python3 code to demonstrate
# Minimum Pair Sum
# using list comprehension + nsmallest() + combinations() + lambda
from itertools import combinations
from heapq import nsmallest

# initializing list
test_list = [3, 4, 1, 7, 9, 8]

# printing original list
print("The original list : " + str(test_list))

# using list comprehension + nsmallest() + combinations() + lambda
# Minimum Pair Sum
# computes 2 min sum pair
res = nsmallest(2, combinations(test_list, 2), key = lambda sub: abs(sub[0] + sub[1]))

# print result
print("The minimum sum pair is : " + str(res))

Output :

The original list : [3, 4, 1, 7, 9, 8]
The minimum sum pair is : [(3, 1), (4, 1)]