'''

public class Solution {

// O(n)

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

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

if (nums == null || nums.length == 0) {

return result;

}

```
for(int i = 0; i < nums.length; i++) {
int val = Math.abs(nums[i]) - 1;
if (nums[val] < 0) {
continue;
}
nums[val] = nums[val] * -1;
}
for(int i = 0; i < nums.length; i++) {
if (nums[i] > 0) {
result.add(i + 1);
}
}
return result;
}
```

}

'''