Python – Maximum Aggregation Pair in List

Sometimes, we need to find the specific problem of getting the pair which yields the maximum 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 + max() + 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 max function to get the maximum sum, combination function finds all sums internally and lambda function is used to compute the sum. 

Python3

# Python3 code to demonstrate
# Maximum Aggretation Pair in List
# using list comprehension + max() + 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 + max() + combinations() + lambda
# Maximum Aggretation Pair in List
res = max(combinations(test_list, 2), key = lambda sub: sub[0] + sub[1])

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

Output : 

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

Time Complexity: O(n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(1), constant extra space is required

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

Python3

# Python3 code to demonstrate
# Maximum Aggretation Pair in List
# using list comprehension + nlargest() + combinations() + lambda
from itertools import combinations
from heapq import nlargest

# 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
# Maximum Aggretation Pair in List
# computes 2 max sum pair
res = nlargest(2, combinations(test_list, 2), key = lambda sub: sub[0] + sub[1])

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

Output : 

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