0442_Find_All_Duplicates_in_an_Array.py

class Solution:
    def findDuplicates(self, nums: List[int]) -> List[int]:
        sol = []

        n = len(nums)

        for num in nums:
            num = abs(num)
            if nums[num-1] < 0:
                sol.append(num)
            nums[num - 1] *= -1
        return sol