Friendship String

Problem Overview

• Compute the lexicographically smallest string from a digit string by repeatedly removing digit d and inserting min(d+1,9) anywhere.
• Input: t test cases; each has digit string s (leading zeros allowed). Output: smallest achievable string per test.
• Constraints: 1<=t<=1e4; 1<=|s|<=2e5; sum |s|<=2e5.
• Context: friendship game focusing on string manipulation and lexicographic order.
• Source: Rubrik interviews; a coding interview problem and common interview question.