n items each belonging to zero or one of
m groups where
group[i] is the group that the
i-th item belongs to and it's equal to
-1 if the
i-th item belongs to no group. The items and the groups are zero indexed. A group can have no item belonging to it.
Return a sorted list of the items such that:
beforeItems[i]is a list containing all the items that should come before the
i-th item in the sorted array (to the left of the
Return any solution if there is more than one solution and return an empty list if there is no solution.
Input: n = 8, m = 2, group = [-1,-1,1,0,0,1,0,-1], beforeItems = [,,,,[3,6],,,] Output: [6,3,4,1,5,2,0,7]
Input: n = 8, m = 2, group = [-1,-1,1,0,0,1,0,-1], beforeItems = [,,,,,,,] Output:  Explanation: This is the same as example 1 except that 4 needs to be before 6 in the sorted list.
1 <= m <= n <= 3 * 104
group.length == beforeItems.length == n
-1 <= group[i] <= m - 1
0 <= beforeItems[i].length <= n - 1
0 <= beforeItems[i][j] <= n - 1
i != beforeItems[i][j]
beforeItems[i]does not contain duplicates elements.