Stamping The Sequence

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 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?".
• 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; that is, you cannot place stamp at index 3 of s in the example above.

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.