haskell: add p3

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

haskell/Lib.hs

@@ -1,4 +1,13 @@
-module Lib where
+module Lib (fib, primeFactors) where
 
-fib :: [ Integer ]
+fib :: [Integer]
 fib = 1 : 2 : zipWith (+) fib (tail fib)
+
+primeFactors :: Integer -> [Integer]
+primeFactors n = genPrimeFactors n 2
+  where
+    genPrimeFactors :: Integer -> Integer -> [Integer]
+    genPrimeFactors n c
+      | c == n = [n]
+      | mod n c /= 0 = genPrimeFactors n (c + 1)
+      | otherwise = c : genPrimeFactors (div n c) c

haskell/p3.hs

@@ -0,0 +1,7 @@
+import Lib (primeFactors)
+
+main :: IO ()
+main = putStr $ show solve
+
+solve :: Integer
+solve = last $ primeFactors 600851475143

rust/Cargo.toml

@@ -2,3 +2,11 @@
 name = "eulerfunt"
 version = "0.1.0"
 edition = "2021"
+
+[[bin]]
+name = "p1"
+path = "./src/p1.rs"
+
+[[bin]]
+name = "p2"
+path = "./src/p2.rs"

rust/gentoml

@@ -10,9 +10,7 @@ version = "0.1.0"
 edition = "2021"
 EOF
 
-if ! [ -e ./src/p*.rs ]; then
-    exit 0
-fi
+[[ ! $(ls ./src/p*.rs) ]] && exit 0
 
 for problem in ./src/p*.rs; do
   file=${problem##*/}

rust/src/lib.rs

@@ -0,0 +1,11 @@
+pub fn fib_till(lim: u32) -> Vec<u32> {
+    let mut ret: Vec<u32> = vec![1, 2];
+    let mut n: usize = 2;
+
+    while ret[n - 1] <= lim {
+        ret.push(ret[n - 1] + ret[n - 2]);
+        n += 1;
+    }
+
+    ret
+}

rust/src/p1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    let multiple_sum = |x| (x..1000).step_by(x).into_iter().sum::<usize>();
+    print!("{}", multiple_sum(3) + multiple_sum(5) - multiple_sum(15));
+}

rust/src/p2.rs

@@ -0,0 +1,6 @@
+use eulerfunt::fib_till;
+
+fn main() {
+    let evenfib = fib_till(4000000).into_iter().filter(|x| x % 2 == 0);
+    print!("{}", evenfib.sum::<u32>());
+}