day 4 part 1 (in Rust)

src/main.rs

@@ -1,86 +1,29 @@
 use anyhow::Result;
-use fancy_regex::Regex;
-use std::{collections::HashMap, io::stdin};
-
-fn is_gear(x: i32, y: i32, lines: &[&[u8]]) -> bool {
-    if x < 0 {
-        return false;
-    }
-    if y < 0 {
-        return false;
-    }
-    if y as usize >= lines.len() {
-        return false;
-    }
-    let line = &lines[y as usize];
-    if x as usize >= line.len() {
-        return false;
-    }
-    if line[x as usize] == b'*' {
-        return true;
-    }
-    false
-}
-
-fn find_gears(x: i32, y: i32, len: i32, lines: &[&[u8]]) -> Vec<(i32, i32)> {
-    let mut v = vec![];
-    for cx in (x - 1)..(x + len) {
-        if is_gear(cx, y - 1, lines) {
-            v.push((cx, y - 1));
-        }
-    }
-    for cy in (y - 1)..=y {
-        if is_gear(x + len, cy, lines) {
-            v.push((x + len, cy));
-        }
-    }
-    for cx in x..=(x + len) {
-        if is_gear(cx, y + 1, lines) {
-            v.push((cx, y + 1));
-        }
-    }
-    for cy in y..=(y + 1) {
-        if is_gear(x - 1, cy, lines) {
-            v.push((x - 1, cy));
-        }
-    }
-    v
-}
+use std::{collections::HashSet, io::stdin};
 
 fn main() -> Result<()> {
-    let num_re = Regex::new(r"(\d+)")?;
-
     let mut sum = 0;
-    let lines: Vec<String> = stdin().lines().map_while(Result::ok).collect();
-    let raw_lines: Vec<&[u8]> = lines.iter().map(|s| s.as_bytes()).collect();
 
-    let mut gear_map: HashMap<(i32, i32), Vec<i32>> = HashMap::new();
+    for line in stdin().lines().map_while(Result::ok) {
+        let p: Vec<_> = line.split(':').collect();
+        let nums: Vec<_> = p[1].split('|').collect();
 
-    for (lineno, line) in lines.iter().enumerate() {
-        for m in num_re.captures_iter(line) {
-            let m = m?;
-            let num_match = m.get(1).unwrap();
-            let num_text = num_match.as_str();
-            let num: i32 = num_text.parse()?;
-            let gears = find_gears(
-                num_match.start() as i32,
-                lineno as i32,
-                num_text.len() as i32,
-                &raw_lines,
-            );
-            for gear in gears {
-                let e = gear_map.entry(gear).or_default();
-                e.push(num);
-            }
-        }
+        let winning: HashSet<i32> = nums[0]
+            .split_whitespace()
+            .map(str::parse)
+            .map_while(Result::ok)
+            .collect();
+
+        let mine: HashSet<i32> = nums[1]
+            .split_whitespace()
+            .map(str::parse)
+            .map_while(Result::ok)
+            .collect();
+
+        let both = winning.intersection(&mine);
+        let c = both.count();
+        sum += if c > 0 { 2i32.pow(c as u32 - 1) } else { 0 };
     }
-    for v in gear_map.values() {
-        if v.len() == 2 {
-            sum += v.iter().product::<i32>();
-        }
-    }
-
     println!("{sum}");
-
     Ok(())
 }