day03

6 files changed, 424 insertions, 0 deletions

diff --git a/2020/.gitignore b/2020/.gitignore
new file mode 100644
index 0000000..2f7896d
--- /dev/null
+++ b/2020/.gitignore
@@ -0,0 +1 @@
+target/
diff --git a/2020/day03/Cargo.lock b/2020/day03/Cargo.lock
new file mode 100644
index 0000000..21c74cb
--- /dev/null
+++ b/2020/day03/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day03"
+version = "0.1.0"
diff --git a/2020/day03/Cargo.toml b/2020/day03/Cargo.toml
new file mode 100644
index 0000000..2804bab
--- /dev/null
+++ b/2020/day03/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day03"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/2020/day03/input0.txt b/2020/day03/input0.txt
new file mode 100644
index 0000000..077fb5f
--- /dev/null
+++ b/2020/day03/input0.txt
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diff --git a/2020/day03/src/main.rs b/2020/day03/src/main.rs
new file mode 100644
index 0000000..6e74f74
--- /dev/null
+++ b/2020/day03/src/main.rs
@@ -0,0 +1,74 @@
+fn slide(lines: Vec<Vec<char>>, vx: i32, vy: i32) -> i32 {
+    let mut x: i32 = 0;
+    let mut y: i32 = 0;
+    let mut hits: i32 = 0;
+    loop {
+        if lines[y as usize][x as usize] == '#' {
+            hits += 1;
+        }
+        x += vx;
+        y += vy;
+        if y as usize >= lines.len() {
+            break;
+        }
+        if x as usize >= lines[y as usize].len() {
+            x -= lines[y as usize].len() as i32;
+        }
+    }
+    hits
+}
+
+fn slide_everywhere(lines: Vec<Vec<char>>) -> i32 {
+    let mut hits: i32 = 1;
+    for (vx, vy) in vec![(1, 1), (3, 1), (5, 1), (7, 1), (1, 2)] {
+        hits *= slide(lines.clone(), vx, vy);
+    }
+    hits
+}
+
+fn main() {
+    let lines: Vec<Vec<char>> = include_str!("../input0.txt")
+        .trim()
+        .split("\n")
+        .map(|s| s.chars().collect())
+        .collect();
+    let hits = slide(lines.clone(), 3, 1);
+    println!("hits: {}", hits);
+    let hits_everything = slide_everywhere(lines.clone());
+    println!("hits on the five paths: {}", hits_everything);
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+
+    #[test]
+    fn small_input() {
+        let lines: Vec<Vec<char>> = include_str!("../test0.txt")
+            .trim()
+            .split("\n")
+            .map(|s| s.chars().collect())
+            .collect();
+        assert_eq!(slide(lines, 3, 1), 7);
+    }
+
+    #[test]
+    fn big_input() {
+        let lines: Vec<Vec<char>> = include_str!("../input0.txt")
+            .trim()
+            .split("\n")
+            .map(|s| s.chars().collect())
+            .collect();
+        assert_eq!(slide(lines, 3, 1), 220);
+    }
+
+    #[test]
+    fn small_input_all_slopes() {
+        let lines: Vec<Vec<char>> = include_str!("../test0.txt")
+            .trim()
+            .split("\n")
+            .map(|s| s.chars().collect())
+            .collect();
+        assert_eq!(slide_everywhere(lines), 336);
+    }
+}
diff --git a/2020/day03/test0.txt b/2020/day03/test0.txt
new file mode 100644
index 0000000..7e88cdc
--- /dev/null
+++ b/2020/day03/test0.txt
@@ -0,0 +1,11 @@
+..##.......
+#...#...#..
+.#....#..#.
+..#.#...#.#
+.#...##..#.
+..#.##.....
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+.#........#
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+.#..#...#.#