# Number Letter Counts

```# Number letter counts
#
# 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?
#
# https://projecteuler.net/problem=17

words = {
1: 'one',
2: 'two',
3: 'three',
4: 'four',
5: 'five',
6: 'six',
7: 'seven',
8: 'eight',
9: 'nine',
10: 'ten',
11: 'eleven',
12: 'twelve',
13: 'thirteen',
14: 'fourteen',
15: 'fifteen',
16: 'sixteen',
17: 'seventeen',
18: 'eighteen',
19: 'nineteen',
20: 'twenty',
30: 'thirty',
40: 'forty',
50: 'fifty',
60: 'sixty',
70: 'seventy',
80: 'eighty',
90: 'ninety',
100: 'hundred',
1000: 'thousand'
}

def parse_number(word_lst, n):
number = str(n)
size = len(number) - 1
for i in range(len(number)):
digit = number[i]
# convert to teens
if size == 1 and int(digit + number[i + 1]) in words:
if i > 0: word_lst.append('and')
word_lst.append(words[int(digit + number[i + 1])])
break
# convert to tens
elif size == 1 and int(digit + '0') in words:
if i > 0: word_lst.append('and')
word_lst.append(words[int(digit + '0')])
else:
if int(digit) > 0:
word_lst.append(words[int(digit)])
# thousands
if size == 3:
word_lst.append(words[1000])
break
# hundreds
if size == 2:
word_lst.append(words[100])
size -= 1
return word_lst

assert parse_number([], 342) == ['three', 'hundred', 'and', 'forty', 'two']
assert parse_number([], 115) == ['one', 'hundred', 'and', 'fifteen']

assert sum(list(map(len, parse_number([], 342)))) == 23
assert sum(list(map(len, parse_number([], 115)))) == 20

# numbers = []
letters = 0
n = 1
while n < len(range(1000)) + 1:
# number = parse_number([], n)
# numbers.append(number)
letters += sum(list(map(len, parse_number([], n))))
n += 1

print(letters)
# 21124
```