day09 part 1

src/main.rs

@@ -1,4 +1,4 @@
 fn main() {
-    aoc_2018::tasks::day08::both();
+    aoc_2018::tasks::day09::task1();
     // aoc_2018::tasks::day08::task2();
 }

src/tasks/day09.rs

@@ -0,0 +1,36 @@
+const PLAYERS: usize = 468;
+const MODULO: usize = 23;
+const HIGHEST_MARBLE: usize = 71843;
+
+pub fn task1() {
+    let mut player_score = [0usize; PLAYERS];
+    let mut current_player = 1;
+    let mut current_index: usize = 0;
+    let mut deck: Vec<usize> = Vec::new();
+    deck.push(0);
+    for marble in 1..=HIGHEST_MARBLE {
+        if marble % MODULO == 0 {
+            current_index = rem(current_index, 7, deck.len());
+            player_score[current_player] += marble;
+            player_score[current_player] += deck.remove(current_index);
+        } else {
+            current_index = (current_index + 2) % deck.len();
+            deck.insert(current_index, marble);
+        }
+        current_player = (current_player + 1) % PLAYERS;
+    }
+
+    let result = player_score.iter().max().unwrap();
+    println!("The highest score is {}", result); // 385469 too low
+}
+
+pub fn rem(a: usize, sub: usize, m: usize) -> usize {
+    if sub > a {
+        let mut x = a as isize;
+        x -= sub as isize;
+        x = x % m as isize;
+        (x + m as isize) as usize
+    } else {
+        (a - sub) % m
+    }
+}

src/tasks/mod.rs

@@ -6,3 +6,4 @@ pub mod day05;
 pub mod day06;
 pub mod day07;
 pub mod day08;
+pub mod day09;