Find the missing element in an unsorted array where every element?
Answer: ppears twice except one public int SingleNumber(int[] nums) { int result = 0; foreach (var num in nums) { result ^= num; } return result; } Explanation: XOR of all elements cancels duplicates, leaving the single unique element.
What interviewers expect
- A clear definition tied to Coding in C# Coding Interview projects
- Trade-offs (performance, maintainability, security, cost)
- When you would and would not use it in production
Real-world example
In a production C# Coding Interview application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.
How to explain in the interview
- Define the concept in one or two sentences.
- Context — where it fits in C# Coding Interview architecture.
- Example — a specific project, bug, or performance win.
- Trade-off — what you gain vs what you sacrifice.
Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.