Closest latency pairs by minimum absolute difference

A monitoring service records latency readings (whole milliseconds) and wants to flag readings that are suspiciously close to one another.

Implement min_abs_diff_pairs(latencies: list[int]) -> list[list[int]].

• Let d be the smallest value of |a - b| over all pairs of readings taken from two different positions in the array.
• Return every pair of values [a, b] with a <= b and b - a == d.
• Sort the result in ascending order by a, then by b.
• Readings can repeat. In that case d is 0. List each repeated value once as [v, v], not once for each pair of positions.
• Return [] if there are fewer than two readings.

Constraints: 0 <= len(latencies) <= 10^5; -10^9 <= latencies[i] <= 10^9.

Example 1

Input:  [40, 12, 31, 18, 33]
Output: [[31, 33]]

The smallest gap is 2, and only 31 and 33 are that close.

Example 2

Input:  [9, 9, 3, 3, 3, 20]
Output: [[3, 3], [9, 9]]

Repeated readings make the smallest gap 0, so each repeated value is listed once.

Start with a simple approach, then improve it. Be ready to discuss repeated values and streaming input.

Reconstructed from the reported question; details may differ from what interviewers ask.