Min Cost to Remove Subsequence

Problem Overview

• Determine the minimum total cost to remove characters so that no permutation of password contains reference as a subsequence.
• Inputs: password string, reference string, and cost[26] mapping 'a'-'z'; Output: a long integer minimum cost.
• Constraints: lowercase letters; lengths up to 1e5; nonnegative per-letter costs.
• Real-world context: Amazon password strength feature; asked in Amazon interviews as a coding interview problem and interview question.