Solve Project Euler 20

flake.nix

@@ -78,6 +78,8 @@
         ] ++ (with pkgs; [
           # Scripts
           clean
+
+          go
         ]);
 
         shellHook = ''

src/l33tcode/841.go

@@ -0,0 +1,41 @@
+package main
+
+import "fmt"
+
+func main() {
+	res := canVisitAllRooms([][]int{{1}, {2}, {}})
+	fmt.Printf("%+v\n", res)
+}
+
+func canVisitAllRooms(rooms [][]int) bool {
+	if len(rooms) > 0 && len(rooms[0]) == 0 {
+			return false
+	}
+
+	keys := getAllKeys(0, make(map[int]struct{}), rooms)
+	keys[0] = struct{}{}    
+
+	for i := 0; i < len(rooms); i++ {
+			if _, ok := keys[i]; !ok {
+					return false
+			}
+	}
+	return true
+}
+
+func getAllKeys(index int, seen map[int]struct{}, rooms [][]int) map[int]struct{} {
+	keys := map[int]struct{}{}
+
+	for j := 0; j < len(rooms[index]); j++ {
+			if _, ok := keys[rooms[index][j]]; ok {
+					continue
+			}
+			keys[rooms[index][j]] = struct{}{}
+			insideKeys := getAllKeys(j, keys, rooms)
+			for k := range insideKeys {
+					keys[k] = struct{}{}
+			}
+	}
+	
+	return keys
+}

src/projectEuler/question20.hs

@@ -0,0 +1,18 @@
+{-
+n! means n x (n - 1) x ... x 3 x 2 x 1.
+For example, 10! = 10 x 9 x ... x 3 x 2 x 1 = 3628800,
+  and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.
+Find the sum of the digits in the number 100!.
+-}
+
+import           Data.Char (digitToInt)
+
+read' :: Integer -> String
+read' = show
+
+main :: IO ()
+main = do
+  print $ "Answer: " <> show ans
+
+ans :: Int
+ans = sum $ map digitToInt $ read' $ product [1..100]