Minimum Prefix Length to Form a Permutation

Problem Given a string s of digits and an array arr[] of digit strings, for each arr[i] compute res[i] = the length of the shortest prefix of s whose characters (as a multiset) cover all characters of arr[i]; -1 if the whole of s doesn't suffice.

Input / Output

• Input: string s, string[] arr (all chars '0'–'9').
• Output: int[] res.

Constraints

• |s| and total query length up to 10^5 — per-query rescans of s are fine only if bounded; precomputation makes queries O(alphabet).

Example

• s = "471247", arr = ["124"] → 4 (prefix "4712" covers {1,2,4}).