This question on StackOverflow asked about how to find the largest 100 items in a very long list: http://stackoverflow.com/questions/1602998/fastest-way-to-obtain-the-largest... I replied that you could do it with something like this (but here taking the k smallest to strip out some irrelevant complications):
takeLargest k = take k . sort
Because "sort" is lazily evaluated this only does enough sorting to find the first k elements. I guess the complexity is something like O(n*k*log(k)). But of equal practical interest is the space complexity. The optimum algorithm is to take the first k items, sort them, and then iterate through the remaining items by adding each item to the sorted list and then throwing out the highest one. That has space complexity O(k). What does the function above do? Paul.