HR scheduled a technical phone interview for a specific date. The interviewer did not call, nor did they send an email to state they were unable to attend.

I emailed HR to inform them that the interviewer missed the interview. They rescheduled, and the interviewer called the second time.

This initial phone interview was simple; they asked about my previous work experience and some basic questions about OOP. Shortly after, I received an email confirming an onsite interview. They booked the flight and sent all the details.

Three days before the onsite interview, they left a voicemail stating the interview was cancelled without providing a reason.

How would you implement a hash function for a particular data structure?