From 91a8d44801ddaba325399435117385c62126a03a Mon Sep 17 00:00:00 2001
From: Daniele Fucini <dfucini@gmail.com>
Date: Thu, 21 Nov 2024 22:00:18 +0100
Subject: [PATCH] Add Haskell solution for Problem 34

---
 Haskell/p034.hs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 Haskell/p034.hs

diff --git a/Haskell/p034.hs b/Haskell/p034.hs
new file mode 100644
index 0000000..89544f4
--- /dev/null
+++ b/Haskell/p034.hs
@@ -0,0 +1,23 @@
+-- 145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
+--
+-- Find the sum of all numbers which are equal to the sum of the factorial of their digits.
+--
+-- Note: as 1! = 1 and 2! = 2 are not sums they are not included.
+
+import Data.Char
+
+factorial :: (Integral a) => a -> a
+factorial 0 = 1
+factorial n = n * factorial (n - 1)
+
+factDigits :: [Int]
+factDigits = map factorial [0..9]
+
+equalsDigitFactorial :: Int -> Bool
+equalsDigitFactorial n = let fact_digit_sum = sum $ [ factDigits !! x | x <- map digitToInt (show n) ]
+                         in fact_digit_sum == n
+
+main = do
+    let result = sum $ filter equalsDigitFactorial [10..9999999]
+    putStrLn $ "Project Euler, Problem 34\n"
+        ++ "Answer: " ++ show result