day three part two

three/Cargo.toml

@@ -7,9 +7,9 @@ edition = "2021"
 name = "pone"
 path = "src/one.rs"
 
-# [[bin]]
-# name = "ptwo"
-# path = "src/two.rs"
+[[bin]]
+name = "ptwo"
+path = "src/two.rs"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 

three/src/two.rs

@@ -1,8 +1,116 @@
-use std::io::{self, Read};
+use std::{
+    collections::HashMap,
+    io::{self, Read},
+};
 
 fn main() {
     let mut buf = String::new();
     io::stdin().read_to_string(&mut buf).unwrap();
 
     let lines: Vec<String> = buf.lines().map(ToOwned::to_owned).collect();
+
+    let line_number_indecies: Vec<_> = lines.iter().map(get_numbers).collect();
+
+    // tuple of the line number and character indexes for our list of lines
+    let numbers = line_number_indecies
+        .iter()
+        .enumerate()
+        .flat_map(|(line, idxs)| {
+            idxs.iter()
+                .map(AsRange::as_range)
+                .zip(std::iter::repeat(line))
+        });
+
+    let mut star_counter: HashMap<(usize, usize), Vec<NumberPos>> = HashMap::new();
+    for (positions, line) in numbers.clone() {
+        if let Some((star_line, star_pos, number)) = is_near_star(&lines, line, positions.clone()) {
+            star_counter
+                .entry((star_line, star_pos))
+                .and_modify(|numbers| numbers.push(number.clone()))
+                .or_insert(Vec::from([number]));
+        }
+    }
+
+    let total: usize = star_counter
+        .values_mut()
+        .filter(|numbers| numbers.len() == 2)
+        .map(|numbers| {
+            numbers
+                .iter()
+                .map(|(positions, line)| &lines[*line][positions.clone()])
+                .flat_map(str::parse::<usize>)
+                .product::<usize>()
+        })
+        .sum();
+
+    print!("{total}");
+}
+
+type NumberPos = (std::ops::Range<usize>, usize);
+
+fn get_numbers<S>(s: S) -> Vec<(usize, usize)>
+where
+    S: AsRef<str>,
+{
+    let s = s.as_ref();
+
+    let mut number_indecies = Vec::new();
+
+    let mut idx = 0;
+    while idx < s.len() {
+        if s.chars().nth(idx).unwrap().is_ascii_digit() {
+            let start_index = idx;
+            while idx < s.len() && s.chars().nth(idx).unwrap().is_ascii_digit() {
+                idx += 1;
+            }
+            let end_index = idx;
+
+            number_indecies.push((start_index, end_index));
+        } else {
+            idx += 1;
+        }
+    }
+
+    number_indecies
+}
+
+trait AsRange {
+    fn as_range(&self) -> std::ops::Range<usize>;
+}
+
+impl AsRange for (usize, usize) {
+    fn as_range(&self) -> std::ops::Range<usize> {
+        self.0..self.1
+    }
+}
+
+fn is_near_star(
+    source: &Vec<String>,
+    number_line: usize,
+    number_positions: std::ops::Range<usize>,
+) -> Option<(usize, usize, NumberPos)> {
+    let mut star = None;
+    'outer: for line in clamp_range(fuzz_range(number_line..number_line + 1), source.len()) {
+        for position in clamp_range(fuzz_range(number_positions.clone()), source[line].len()) {
+            match source[line].chars().nth(position).unwrap() {
+                '*' => {
+                    star = Some((position, line, (number_positions, number_line)));
+                    break 'outer;
+                }
+                _ => (),
+            }
+        }
+    }
+
+    star
+}
+
+fn clamp_range(input: std::ops::Range<usize>, max: usize) -> std::ops::Range<usize> {
+    let end = if input.end > max { max } else { input.end };
+
+    input.start..end
+}
+
+fn fuzz_range(input: std::ops::Range<usize>) -> std::ops::Range<usize> {
+    input.start.checked_sub(1).unwrap_or(input.start)..input.end + 1
 }