936 - Stamping The Sequence.

Hard

You are given two strings stamp and target. Initially, there is a string s of length target.length with all s[i] == '?'.

In one turn, you can place stamp over s and replace every letter in the s with the corresponding letter from stamp.

• For example, if stamp = "abc" and target = "abcba", then s is "?????" initially. In one turn you can:

  • place stamp at index 0 of s to obtain "abc??",

  • place stamp at index 1 of s to obtain "?abc?", or

  • place stamp at index 2 of s to obtain "??abc".

  Note that stamp must be fully contained in the boundaries of s in order to stamp (i.e., you cannot place stamp at index 3 of s).

We want to convert s to target using at most 10 * target.length turns.

Return an array of the index of the left-most letter being stamped at each turn. If we cannot obtain target from s within 10 * target.length turns, return an empty array.

Example 1:

Input: stamp = "abc", target = "ababc"

Output: 0,2

Explanation: Initially s = "?????".

• Place stamp at index 0 to get "abc??".

• Place stamp at index 2 to get "ababc".

1,0,2 would also be accepted as an answer, as well as some other answers.

Example 2:

Input: stamp = "abca", target = "aabcaca"

Output: 3,0,1

Explanation: Initially s = "???????".

• Place stamp at index 3 to get "???abca".

• Place stamp at index 0 to get "abcabca".

• Place stamp at index 1 to get "aabcaca".

Constraints:

• 1 <= stamp.length <= target.length <= 1000

• stamp and target consist of lowercase English letters.