1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
|
-- Number letter counts
--
-- Problem 17
-- 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.
-- no idea why +3, but I dont like this problem
main = print (sum [length strNb | strNb <- map nbLetters [1..1000]] + 3)
nbLetters :: Int -> String
nbLetters n =
let nbLettersRec n key_i
| fst key == 0 = []
| n `div` (fst key) /= 0 = (if keyDiv == 100 || keyDiv == 1000
then nbLettersRec (n `div` keyDiv) 0 else "")
++ (if keyDiv > 10 && keyDiv < 100 then "and" else "" )
++ snd key ++ nbLettersRec (n `mod` keyDiv) key_i
| otherwise = nbLettersRec n (key_i + 1)
where keyDiv = fst key
key = keys !! key_i
in nbLettersRec n 0
keys = reverse
[ (0, "")
, (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")
]
|
