done.md

import Data.List (nub, permutations)
let a = [ [a, b, c] | a <- [1..9], b <- [1..9], c <- [1..9], a <= b, b <= c, a + b + c == 21]
let comb = nub $ concatMap permutations a
forM_ comb (\[a,b,c] -> putStrLn $ "(" <> show a <> ", " <> show b <> " ," <> show c <> ")\\")
forM_ a (\[a,b,c] -> putStrLn $ "(" <> show a <> ", " <> show b <> " ," <> show c <> ")\\")
length comb
28
length a
7

順列(28)

(3, 9 ,9)
(9, 3 ,9)
(9, 9 ,3)
(4, 8 ,9)
(8, 4 ,9)
(9, 8 ,4)
(8, 9 ,4)
(9, 4 ,8)
(4, 9 ,8)
(5, 7 ,9)
(7, 5 ,9)
(9, 7 ,5)
(7, 9 ,5)
(9, 5 ,7)
(5, 9 ,7)
(5, 8 ,8)
(8, 5 ,8)
(8, 8 ,5)
(6, 6 ,9)
(9, 6 ,6)
(6, 9 ,6)
(6, 7 ,8)
(7, 6 ,8)
(8, 7 ,6)
(7, 8 ,6)
(8, 6 ,7)
(6, 8 ,7)
(7, 7 ,7)

組み合わせ (7)

(3, 9 ,9)
(4, 8 ,9)
(5, 7 ,9)
(5, 8 ,8)
(6, 6 ,9)
(6, 7 ,8)
(7, 7 ,7)