1 files changed, 33 insertions(+), 7 deletions(-)

M src/days/day03.rs

@@ 8,7 8,7 @@ fn parse_contents(contents: String) -> Vec<Vec<char>> {
     map
 }
 
-fn count_trees(map: &Vec<Vec<char>>) -> i32 {
+fn count_trees(map: &Vec<Vec<char>>, x_add: usize, y_add: usize) -> i32 {
     let mut x = 0;
     let mut y = 0;
     let mut count = 0;


@@ 16,9 16,9 @@ fn count_trees(map: &Vec<Vec<char>>) -> i32 {
     let x_max = map[0].len();
     let y_max = map.len();
 
-    while y != y_max - 1 {
-        y += 1;
-        x = (x + 3) % x_max;
+    while y < y_max - y_add {
+        y += y_add;
+        x = (x + x_add) % x_max;
         if map[y][x] == '#' {
             count += 1;
         }


@@ 26,12 26,30 @@ fn count_trees(map: &Vec<Vec<char>>) -> i32 {
     count
 }
 
+fn calc_solution2(map: &Vec<Vec<char>>) -> i64 {
+    // Using only i32 would cause on overflow
+    let mut product: i64 = 1;
+    let mut count = count_trees(map, 1, 1);
+    product *= count as i64;
+    count = count_trees(map, 3, 1);
+    product *= count as i64;
+    count = count_trees(map, 5, 1);
+    product *= count as i64;
+    count = count_trees(map, 7, 1);
+    product *= count as i64;
+    count = count_trees(map, 1, 2);
+    product *= count as i64;
+    product
+}
+
 pub fn get_solution() {
     let contents = fs::read_to_string("data/day03.dat").expect("Could not read data");
     let map = parse_contents(contents);
-    let count = count_trees(&map);
+    let count = count_trees(&map, 3, 1);
 
-    println!("Day 3, part 1: {}", count);
+    let product = calc_solution2(&map);
+
+    println!("Day 3, part 1: {}, part 2: {}", count, product);
 }
 
 #[cfg(test)]


@@ 42,7 60,15 @@ mod tests {
     fn part1() {
         let contents = fs::read_to_string("data/day03_test.dat").expect("Could not read data");
         let map = parse_contents(contents);
-        let count = count_trees(&map);
+        let count = count_trees(&map, 3, 1);
         assert_eq!(count, 7);
     }
+
+    #[test]
+    fn part2() {
+        let contents = fs::read_to_string("data/day03_test.dat").expect("Could not read data");
+        let map = parse_contents(contents);
+        let product = calc_solution2(&map);
+        assert_eq!(product, 336);
+    }
 }