Shortest Uncommon Substring in an Array

For each string in an array, find the shortest substring that does not occur in any other string (choose the lexicographically smallest one among ties), or return an empty string if none exists. The core challenge is efficiently testing substring uniqueness across all strings — often solved with generalized suffix structures, tries, or rolling-hash enumeration given n ≤ 100 and each length ≤ 20.