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AI-assisted engineering/Reviewing AI code

Fix the average of a run of sensor readings

Review the AI's codeEasy10 min

Your task

Your firmware team averages sensor readings that are unsigned 32-bit integers. The first Rust version summed them into a u32, which panics in debug builds and silently wraps around in release builds once the total passes 4294967295. It also divided by zero on an empty list.

An assistant wrote average_reading(readings) to fix both. It is in the editor. It has a bug. Find it and fix it.

Input and output:

  • readings: the readings, each a whole number from 0 to 4294967295.
  • Return the average as an integer, or -1 when there are no readings.

Rules the tests check:

  • An empty list returns -1.
  • Otherwise return the exact sum of all readings divided by their count, rounded down. The sum can be far larger than 4294967295 and must not wrap.

Examples

average_reading(readings: list[int]) -> int
Example 1
Inputaverage_reading([10, 20, 30])
Output20
Example 2
Inputaverage_reading([])
Output-1
Example 3
Inputaverage_reading([4294967295, 4294967295, 4294967295, 4294967295])
Output4294967295