Problem

At Stripe, an existing utility scans a list of integers with nested loops to find values that appear more than once. Rewrite it for better performance.

Implement a function find_duplicates(nums) that returns all distinct duplicate values in ascending order, along with how many times each value appears.

Formal Specification

• Input: nums, a list of integers
• Output: a list of lists, where each element is [value, count] for every integer that appears at least twice
• The result must be sorted by value in ascending order

Examples

Example 1 Input: nums = [4, 1, 2, 1, 2, 2, 5] Output: [[1, 2], [2, 3]]

Explanation: 1 appears 2 times and 2 appears 3 times. Other values appear once.

Example 2 Input: nums = [7, 7, 7, 7] Output: [[7, 4]]

Explanation: Only 7 is duplicated, and it appears 4 times.

Constraints

• 0 <= len(nums) <= 10^5
• -10^9 <= nums[i] <= 10^9
• The function should be efficient enough for large inputs
• If there are no duplicates, return an empty list