3870. Count Commas in Range

Solution →

You are given an integer n.

Return the total number of commas used when writing all integers from [1, n] (inclusive) in standard number formatting.

In standard formatting:

• A comma is inserted after every three digits from the right.
• Numbers with fewer than 4 digits contain no commas.

Example 1

Input: n = 1002
Output: 3
Explanation:
The numbers "1,000", "1,001", and "1,002" each contain one comma, giving a
total of 3.

Example 2

Input: n = 998
Output: 0
Explanation:
All numbers from 1 to 998 have fewer than four digits. Therefore, no commas are
used.

Constraints

• 1 <= n <= 10^5