How to find the maximum product of two elements in a list?

Question

I was trying out a problem on hackerrank contest for fun, and there came this question. I used itertools for this, here is the code:

import itertools

l = []

for _ in range(int(input())):
    l.append(int(input()))


max = l[0] * l[len(l)-1]

for a,b in itertools.combinations(l,2):
    if max < (a*b):
        max = (a*b)
print(max)

Is their any other efficient way than this? As I am getting time out error on some test cases which I cant access (as its a small contest).

Answer 1

Here is an implementation following @User_Targaryen's logic. heapq returns the 2 largest and 2 smallest numbers in the list, mul operator returns the products of these 2 pairs of numbers, and max returns the largest of these 2 products.

>>> import heapq
>>> from operator import mul
>>> l = [2,40,600,3,-89,-899]
>>> max(mul(*heapq.nsmallest(2,l)),mul(*heapq.nlargest(2,l)))
80011
# -899*-89 = 80011