Problem 17 : Number letter counts

Problem Statement

If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.

If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many letters would be used?

NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of “and” when writing out numbers is in compliance with British usage.

Solution

units = ['one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 
'eleven', 'twelve' , 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 
'nineteen']

tens = ['twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety']

other = ['hundred', 'thousand', 'and']

result = 0

for i in range (1, 1001):
  
    unit = i% 10
    ten = (i // 10)% 10
    hundred = (i // 100)% 10
    thousand = (i // 1000)% 10
   
    if thousand != 0:
        result += len (units [0]) + len (other [1])
    if i% 1000 != 0:
        if hundred != 0:
            result += len (units [hundred-1]) + len (other [0])
            if i% 100 != 0:
                result += len (other [2])
        if i% 100 != 0:
            if ten <2:
                result += len (units [i% 100-1])
            else:
                result += len (tens [ten-2])
                if unit != 0:
                    result += len (units [unit-1])
print (result)

Output

21124