3871. Count Commas in Range II
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 <= 1015
Math
Hints
Hint 1
Count the numbers in each comma group (1-3 digits, 4-6 digits, 7-9 digits, ...) and multiply by how many commas each number in that group has.
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