How Many Digits between 1 and N

Challenge Difficulty: Medium | Estimated completion time: ~25 minutes

Imagine you took all the numbers between 0 and n and concatenated them together into a long string.

How many digits are there between 0 and n? Write a function that can calculate this.

There are 0 digits between 0 and 1, there are 9 digits between 0 and 10 and there are 189 digits between 0 and 100.

Examples

digits(1)
output = 0
 
digits(10)
output = 9
 
digits(100)
output = 189
 
digits(2020)
output = 6969

Solution

Python

def digits(number: int) -> int: """Count total digits in all numbers from 1 to number (exclusive). Args: number: Upper bound (exclusive) Returns: Total count of digits """ total = 0 for value in range(1, number): total += len(str(value)) return total if __name__ == "__main__": print(digits(1)) # 0 print(digits(10)) # 9 print(digits(100)) # 189 print(digits(2020)) # 6969

Output