Added 2022, first few problems

3 files changed, 58 insertions, 0 deletions

diff --git a/2022/09/a.rs b/2022/09/a.rs
new file mode 100644
index 0000000..0fc6278
--- /dev/null
+++ b/2022/09/a.rs
@@ -0,0 +1,6 @@
+mod common;
+use common::*;
+
+fn main() {
+    println!("{}", simulate(2).len());
+}
diff --git a/2022/09/b.rs b/2022/09/b.rs
new file mode 100644
index 0000000..1d43500
--- /dev/null
+++ b/2022/09/b.rs
@@ -0,0 +1,6 @@
+mod common;
+use common::*;
+
+fn main() {
+    println!("{}", simulate(10).len());
+}
diff --git a/2022/09/common.rs b/2022/09/common.rs
new file mode 100644
index 0000000..45048da
--- /dev/null
+++ b/2022/09/common.rs
@@ -0,0 +1,46 @@
+use std::collections::HashSet;
+
+fn get_dir(c: char) -> (i64, i64) {
+    match c {
+        'R' => (1, 0),
+        'L' => (-1, 0),
+        'U' => (0, 1),
+        'D' => (0, -1),
+        _ => panic!("Unexpected char")
+    }
+}
+
+fn follow(lead: (i64, i64), trail: (i64, i64)) -> (i64, i64) {
+    let max1 = |x: i64| x / (2 - (x%2).abs());
+    let d = (max1(lead.0 - trail.0), max1(lead.1 - trail.1));
+    (trail.0 + d.0, trail.1 + d.1)
+}
+
+fn step(r: &mut Vec<(i64, i64)>, d: (i64, i64)) {
+    r[0] = (r[0].0 + d.0, r[0].1 + d.1);
+    for i in 1..r.len() {
+        if (r[i].0 - r[i-1].0).abs() > 1 || (r[i].1 - r[i-1].1).abs() > 1 {
+            r[i] = follow(r[i-1], r[i]);
+        } else {
+            break;
+        }
+    }
+}
+
+pub fn simulate(n: usize) -> HashSet<(i64, i64)> {
+    let mut r = vec![(0, 0); n];
+    let mut visited = HashSet::<(i64, i64)>::new();
+    visited.insert(r[n-1]);
+
+    let mut line = String::new();
+    while std::io::stdin().read_line(&mut line).unwrap() > 0 {
+        let dir = get_dir(line.chars().nth(0).unwrap());
+        let l = line[2..line.len()-1].parse::<usize>().unwrap();
+        for _ in 0..l {
+            step(&mut r, dir);
+            visited.insert(r[n-1]);
+        }
+        line.clear();
+    }
+    visited
+}