Identifying the top k elements pattern

Many problems where we need to find and process the top k items in a fixed-sized dataset or a stream can be solved using the top k technique. These are generally medium or hard problems where we are given a dataset and a function, f and we need to find the aggregated the value of the function f over the top k items in the dataset. While there may be other ways to solve such problems, the technique using a k-sized heap is generally the most efficient.

If the problem statement or its solution follows the generic template below, it can be solved by applying the k-largest-items finding technique.