Your question is Find Duplicate Values in Array. Start with the requirements on the right.
Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.
Given an integer array nums, return all values that appear more than once. Each duplicate should appear only once in the output, in the order it is first detected as a repeat during a left-to-right scan.
1 <= len(nums) <= 10^5-10^9 <= nums[i] <= 10^9