Set Mismatch
Easy · hash map
A ticket machine should have printed each of the numbers 1 to n exactly once. Because of a fault, one number was printed twice and, as a result, one other number was never printed. The n printed numbers are in the list nums, in no particular order.
Return a list of two integers: first the number that appears twice, then the number that is missing.
Examples
Example 1
Input: nums = [1, 2, 2, 4]
Output: [2, 3]
2 appears twice and 3 never appears.
Example 2
Input: nums = [3, 1, 3]
Output: [3, 2]
3 appears twice and 2 never appears.
Example 3
Input: nums = [2, 2]
Output: [2, 1]
Constraints
- 2 <= len(nums) <= 3000
- 1 <= nums[i] <= len(nums)
- Exactly one number appears twice, exactly one number from 1 to len(nums) is missing, and every other number appears once.