This is a fibonacci-heap priority-queue implementation. That means insert: O(1) decrease_priority: Amortized O(1) delete_min: Amortized O(log n) This project is different from K. Kodamas PQueue in that it allows a decrease key operation. That makes PriorityQueue usable for algorithms like dijkstras shortest path algorithm, while PQueue is more suitable for Heapsort and the like.