day 3 solution

2020/day_3/src/main.rs

@@ -0,0 +1,37 @@
+fn main() {
+    let mut hill: Vec<String> = Vec::new();
+    let contents = std::fs::read_to_string("input1").unwrap();
+    for s in contents.lines() {
+        hill.push(s.parse::<String>().unwrap());
+    }
+
+    let rounds = [[1, 1], [3, 1], [5, 1], [7, 1], [1, 2]];
+    // let rounds = [[1, 2]];
+    let mut hit_trees = Vec::new();
+    for r in rounds.iter() {
+        let right_rule = r[0];
+        let down_rule = r[1];
+        let mut right_pos = 0;
+        let mut down_pos = 0;
+        let mut trees: i64 = 0;
+        loop {
+            for _ in 0..right_rule {
+                if right_pos == hill[down_pos].len() - 1 {
+                    right_pos = 0;
+                } else {
+                    right_pos += 1;
+                }
+            }
+            down_pos += down_rule;
+            if hill[down_pos].chars().nth(right_pos).unwrap() == '#' {
+                trees += 1;
+            }
+            if hill.len() - 1 == down_pos {
+                break;
+            }
+        }
+        hit_trees.push(trees);
+    }
+    let total = hit_trees[0] * hit_trees[1] * hit_trees[2] * hit_trees[3] * hit_trees[4];
+    print!("You hit {} total trees!\n", total);
+}