Return the value occurring more than half the time; the input contract guarantees one exists.
A good solution should
- State the invariant or decision rule that makes the approach correct.
- Explain time and space costs in terms of input size and required output.
- Handle empty, minimal, duplicate, and boundary-shaped inputs.
Reasoning prompt
Use Boyer-Moore voting and explain the cancellation argument. If the guarantee is removed, add a verification pass.
Use the linked judge for the canonical challenge. The examples above are compact TRT checks; create additional tests around the boundary most likely to break your invariant.