Calculate Total Round-Robin Waiting Time

Question

Each entry of the integer array arr is a task, and its value says how many hours of work that task needs. A single processor runs the tasks in round-robin order, with the queue starting at index 0: whenever a task gets its turn, it is worked on for one hour. Unfinished work sends the task to the back of the line, where it waits for its next turn in the following cycle. The processor never runs two tasks at once, and it keeps cycling until no work remains. ...