Question

It is an interview question.

Given a text file, each line includes : shipment ID , UPC code , quantity

Find the 10 largest quantity lines.

My solutions :

By c++

make a min heap (with size 10) with quantity as compare object.

Read each entry as a struct with field { shipment ID, UPC code, quantity }

Compare it with the top element of the 10-element min-heap,

if > replace the top element with it, else read the next element.

It is O(n lg n).

Space O(1).

Better solutions ?

thanks

Answer 1

Side note: Your time cost is actually O(n), since the per-element insertion time is a constant (O(log 10)).

The basic idea is sound — you won’t do better than O(n) in terms of cost — but rather than rolling your own heap, use std::priority_queue.