Retrieve the two highest item from a list containing 100,000 integers

Question

How can retrieve the two highest item from a list containing 100,000 integers without having to sort the entire list first?

Answer 1

I know this topic is old, but here is a simple solution to this problem. Tested against heapq.nlargest and this is a bit faster (no sorting needed):

Works for both positive and negative numbers.

Function below: Max time used: 0.12, max memory used: 29290496 heapq.nlargest: Max time used: 0.14, max memory used: 31088640

def two_highest_numbers(list_to_work):

    first = None
    second = None

    for number in list_to_work:
        if first is None:
            first = number
        elif number > first:
            second = first
            first = number
        else:
            if second is None:
                second = number
            elif number > second:
                second = number

return [first, second]