Find All Duplicates in an Array
Medium · hash map
A list nums holds n integers, and every integer is between 1 and n (inclusive). No value appears more than twice.
Return every value that appears exactly twice, in ascending order. If no value appears twice, return an empty list.
Examples
Example 1
Input: nums = [5, 1, 5, 3, 3, 6]
Output: [3, 5]
Both 3 and 5 appear twice. The other values appear once.
Example 2
Input: nums = [2, 1, 3]
Output: []
Every value appears once.
Example 3
Input: nums = [2, 2]
Output: [2]
Constraints
- 1 <= len(nums) <= 10^5
- 1 <= nums[i] <= len(nums)
- No value appears more than twice.