```
public class Solution {
public List<Integer> findDisappearedNumbers(int[] nums) {
List<Integer> result = new ArrayList<Integer>();
for(int i = 0; i < nums.length; i++){
int index = Math.abs(nums[i]) - 1;
if(nums[index] > 0)
nums[index] *= -1;
}
for(int i = 0; i < nums.length; i++){
if(nums[i] > 0){
result.add(i+1);
}
}
return result;
}
}
```