Find All Numbers Disappeared in an Array (Leetcode 448)

Problem Link: https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        
        for i in range(len(nums)):
            idx=abs(nums[i])-1
            nums[idx]=-1*abs(nums[idx])
        
        ans=[]
        for i in range(len(nums)):
            if(nums[i]>0):
                ans.append(i+1)
        return ans