Priority Queue:
- https://www.youtube.com/watch?v=wptevk0bshY
- https://www.geeksforgeeks.org/priority-queue-set-1-introduction/
- https://www.geeksforgeeks.org/priority-queue-class-in-java-2/
- https://docs.oracle.com/javase/8/docs/api/java/util/PriorityQueue.html

HashMap:
- https://www.w3schools.com/java/java_hashmap.asp
- https://www.geeksforgeeks.org/java-util-hashmap-in-java-with-examples/
- https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html
- https://www.youtube.com/watch?v=KyUTuwz_b7Q
- https://www.youtube.com/watch?v=wWgIAphfn2U&list=PLqM7alHXFySGwXaessYMemAnITqlZdZVE

Algoritmi i strukture podataka u Java-i
- https://www.youtube.com/watch?v=f5OD9CKrZEw&list=PLGLfVvz_LVvReUrWr94U-ZMgjYTQ538nT