Find All Duplicates in an Array
Given an integer array nums of length n where all the integers of nums are in the range [1, n] and each integer appears at most twice, return an array of all the integers that appear twice.
You must write an algorithm that runs in O(n) time and uses only constant auxiliary space, excluding the space needed to store the output.
Example 1
Input
nums = [4,3,2,7,8,2,3,1]Output
[2,3]The integers 2 and 3 each appear twice in the array.
Example 2
Input
nums = [1,1,2]Output
[1]The integer 1 appears twice in the array.
Constraints
- n == nums.length
- 1 <= n <= 10^5
- 1 <= nums[i] <= n
- Each element in nums appears once or twice.
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