A PriorityQueue is a list that always keeps its items sorted based on some rule, like smallest to largest. So, when you take an item out, you always get the one with the highest (or lowest) priority.

Every so often its good to exercise your brain with a math problem or two that forces you to recall principles you learned ...

The program is expected to return the indices of two numbers that add up to the target. However, it fails to do so correctly in some cases, returning the wrong indices or throwing an exception even ...