import java.util.ArrayList;

import java.util.List;

//https://leetcode.com/problems/find-all-duplicates-in-an-array/

public class FindAllDuplicates {

//Approach:

// As given that numbers in array are postive and in the range of array.length

//while iterating make the value at index as negative before making it negative check if it is already negative means

// it is already visited hence the index would be duplicate value as it is already visited

public List<Integer> findDuplicates(int[] nums) {

List<Integer> res = new ArrayList<>();

for(int i=0;i<nums.length;i++) {

if(nums[Math.abs(nums[i])-1]<0) {

res.add(Math.abs(nums[i]));

} else {

nums[Math.abs(nums[i])-1]*=-1;

}

}

return res;

}

}

//Similar would be the approach for finding all disappeared numbers in the array, while iterating make all values at the

// index as negatives and iterate through the array again to find all postive values and add the indexes into the result