Distinct Digit Numbers

Problem Overview

• Given integer ranges, count how many numbers in each inclusive range have all distinct digits.
• Input: q pairs [n, m]; Output: one count per pair; Constraints: 1 ≤ q ≤ 1e5 and 1 ≤ n ≤ m ≤ 10^6.
• Applies to digit-uniqueness checks in numeric data, such as IDs or codes.
• A Jpmorgan interviews interview question commonly seen in a coding interview.
• Clear counting problem designed for range queries and validation tasks.