External Merge Sort with a Heap

Problem Overview

Citadel Securities phone screen. One candidate for a C++ software engineering role reports that the phone screen was "an external merge sort with a heap". That is the whole description: no input format, sizes or follow-ups were reported. The statement below is the standard textbook problem, set up so you…

• The rest of the problem statement — full requirements, constraints, and edge cases
• Approach and trade-offs — what passing candidates did, and the mistakes that sink people