Leetcode 448 Find All Numbers Disappeared in an Array

public List<Integer> findDisappearedNumbers(int[] nums) {
        List<Integer> res = new ArrayList<>();
        int n = nums.length;
        for (int i = 0; i < nums.length; i ++) nums[(nums[i]-1) % n] += n;
        for (int i = 0; i < nums.length; i ++) if (nums[i] <= n) res.add(i+1);
        return res;
    }