2 files changed, 130 insertions, 2 deletions
diff --git a/src/bin/day2.rs b/src/bin/day2.rs
index 8c5c54d..46abcc9 100644
--- a/src/bin/day2.rs
+++ b/src/bin/day2.rs
@@ -1,6 +1,6 @@
 #![feature(test)]
-use std::str::FromStr;
 use std::error::Error;
+use std::str::FromStr;
 
 const COLORS: [&str; 3] = ["red", "green", "blue"];
 const AMOUNT: [u32; 3] = [12, 13, 14];
@@ -12,7 +12,9 @@ struct HelloWorld {
 impl FromStr for HelloWorld {
     type Err = std::convert::Infallible;
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        Ok(HelloWorld { msg: String::from(s), })
+        Ok(HelloWorld {
+            msg: String::from(s),
+        })
     }
 }
 
diff --git a/src/bin/day3.rs b/src/bin/day3.rs
new file mode 100644
index 0000000..ec8d49b
--- /dev/null
+++ b/src/bin/day3.rs
@@ -0,0 +1,126 @@
+#![feature(test)]
+use std::error::Error;
+use std::str::FromStr;
+extern crate test;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test::Bencher;
+
+    #[bench]
+    fn other(b: &mut Bencher) {
+        b.iter(|| main());
+    }
+}
+
+#[derive(Debug)]
+struct Number {
+    value: u32,
+    begin: usize,
+    end: usize,
+}
+
+#[derive(Debug)]
+struct SchematicLine {
+    numbers: Vec<Number>,
+    symbols: Vec<(usize, char)>,
+}
+
+impl FromStr for SchematicLine {
+    type Err = std::convert::Infallible;
+    fn from_str(line: &str) -> Result<Self, <Self as FromStr>::Err> {
+        let numbers = (1..4).rev().fold(vec![], |mut acc, window_size| {
+            acc.extend(
+                line.as_bytes()
+                    .windows(window_size as usize)
+                    .enumerate()
+                    .filter(|(i, _)| !acc.iter().any(|n: &Number| n.begin <= *i && *i <= n.end))
+                    .filter_map(|(i, w)| {
+                        if w[0] as char == '+' {
+                            return None;
+                        }
+                        if let Some(num) = std::str::from_utf8(w).ok()?.parse().ok() {
+                            Some(Number {
+                                value: num,
+                                begin: i,
+                                end: i + window_size - 1,
+                            })
+                        } else {
+                            None
+                        }
+                    })
+                    .collect::<Vec<_>>(),
+            );
+            acc
+        });
+        let symbols = line
+            .char_indices()
+            .filter(|(_, c)| !c.is_digit(10) && *c != '.')
+            .collect::<Vec<_>>();
+        Ok(SchematicLine { numbers, symbols })
+    }
+}
+
+impl SchematicLine {
+    pub fn check_against_symbols<'a>(&'a self, mut symbols: impl Iterator<Item=&'a (usize, char)> + 'a + Clone) -> impl Iterator<Item=&Number> + 'a {
+        let s = symbols.collect::<Vec<_>>();
+        self.numbers
+            .iter()
+            .filter(move |n| {
+                s.iter().any(|&&(pos, _)| {
+                    (pos as i32 - n.begin as i32).abs() <= 1
+                        || (pos as i32 - n.end as i32).abs() <= 1
+                }) || self
+                    .symbols
+                    .iter()
+                    .find(|&&(s, _)| {
+                        s as isize == n.begin as isize - 1 || s as isize == n.end as isize + 1
+                    })
+                    .is_some()
+            })
+    }
+
+    pub fn get_gear_products(&self, mut numbers:  impl Iterator<Item=&Number>) -> impl Iterator<Item=&u32> {
+        self.symbols
+            .filter(|(i, symbol)| symbol == '*')
+            .map(|(i, _)| i as u32)
+    }
+}
+
+// 467..114..   ...*......   ..35..633.   ......#...
+fn main() -> Result<(), Box<dyn Error>> {
+    let file = std::fs::read_to_string("input/3/in.txt")?;
+    let lines: &[SchematicLine] = &file
+        .lines()
+        .map(|line| line.parse().unwrap())
+        .collect::<Vec<_>>();
+    let numbers = lines
+        .windows(3)
+        .enumerate()
+        .fold(vec![], |mut machine_part_numbers, (i, w)| {
+            if i == 0 {
+                machine_part_numbers
+                    .extend(w[0].check_against_symbols(w[1].symbols.iter()));
+            }
+            machine_part_numbers
+                .extend(w[1].check_against_symbols(w[0].symbols.iter().chain(w[2].symbols.iter())));
+            if i == lines.len() - 3 {
+                machine_part_numbers
+                    .extend(w[2].check_against_symbols(w[1].symbols.iter()));
+            }
+            machine_part_numbers
+        });
+    let part1: u32 = numbers.iter().map(|n| n.value).sum();
+
+    let part2 = lines
+        .windows(3)
+        .enumerate()
+        .fold(vec![], |mut gear_products, (i, w)| {
+            gear_products.extend();
+            gear_products
+        });
+    dbg!(&part2);
+
+    Ok(())
+}