The IndexMinPQ class represents an indexed priority queue of generic keys. It supports the usual Insert and Delete-the-minimum operations, along with Delete and Change-the-key methods. In order to let the client refer to keys on the priority queue, an integer between 0 and maxN-1 is associated with each key-the client uses this integer to specify which key to delete or change. It also supports methods for peeking at the minimum key, testing if the priority queue is empty, and iterating through the keys.

This implementation uses a binary heap along with an array to associate keys with integers in the given range. The Insert, Delete-the-minimum, Delete, Change-key, Decrease-key, and Increase-key operations take logarithmic time. The Is-empty, Count, Min-index, Min-key, and Key-of operations take constant time. Construction takes time proportional to the specified capacity.