1 files changed, 95 insertions, 0 deletions

diff --git a/2021/day5/src/main.rs b/2021/day5/src/main.rs
new file mode 100644
index 0000000..498deb0
--- /dev/null
+++ b/2021/day5/src/main.rs
@@ -0,0 +1,95 @@
+use std::cmp::{max, min};
+use std::collections::HashMap;
+use std::env;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+fn main() {
+    let reader = open_file();
+
+    let mut coords: HashMap<(i32, i32), i32> = HashMap::new();
+
+    for line in reader.lines() {
+        if let Ok(line) = line {
+            let vents = line.split(" -> ").collect::<Vec<&str>>();
+            let first = vents[0].split(",").collect::<Vec<&str>>();
+            let second = vents[1].split(",").collect::<Vec<&str>>();
+
+            let first: Vec<i32> = first.into_iter().map(|s| s.parse().unwrap()).collect();
+            let second: Vec<i32> = second.into_iter().map(|s| s.parse().unwrap()).collect();
+
+            let xstep: i32;
+            let ystep: i32;
+            let start_x = min(first[0], second[0]);
+            let end_x = max(first[0], second[0]);
+            let start_y = min(first[1], second[1]);
+            let end_y = max(first[1], second[1]);
+            let distance = max(end_x - start_x, end_y - start_y);
+
+            if first[0] > second[0] {
+                xstep = -1;
+            } else if first[0] < second[0] {
+                xstep = 1;
+            } else {
+                xstep = 0;
+            }
+
+            if first[1] > second[1] {
+                ystep = -1;
+            } else if first[1] < second[1] {
+                ystep = 1;
+            } else {
+                ystep = 0;
+            }
+
+            for step in 0..=distance {
+                let counter = coords
+                    .entry((first[0] + step * xstep, first[1] + step * ystep))
+                    .or_insert(0);
+                *counter += 1;
+            }
+        }
+    }
+
+    // println!("coords: {:?}", coords);
+    // visualize(&coords);
+
+    let result = coords.iter().filter(|(_, &y)| y >= 2).count();
+    println!("{}", result);
+}
+
+fn visualize(map: &HashMap<(i32, i32), i32>) {
+    let start_x = map.iter().map(|((x, _), _)| x).min().unwrap();
+    let start_y = map.iter().map(|((_, y), _)| y).min().unwrap();
+    let end_x = map.iter().map(|((x, _), _)| x).max().unwrap();
+    let end_y = map.iter().map(|((_, y), _)| y).max().unwrap();
+    println!("start_x: {}", start_x);
+    println!("start_y: {}", start_y);
+    println!("end_x: {}", end_x);
+    println!("end_y: {}", end_y);
+
+    for y in *start_y..=*end_y {
+        for x in *start_x..=*end_x {
+            if let Some(val) = map.get(&(x, y)) {
+                print!("{}", val);
+            } else {
+                print!(".")
+            }
+        }
+        println!("");
+    }
+}
+
+fn open_file() -> BufReader<File> {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 2 {
+        eprintln!("Usage: {} <filename>", args[0]);
+        std::process::exit(1);
+    }
+
+    let filename = &args[1];
+
+    let file = File::open(filename).unwrap_or_else(|_| panic!("No such file: {}", filename));
+    BufReader::new(file)
+}