From 3c0e91576018bc9fe1cae0b4516038b56afcd27a Mon Sep 17 00:00:00 2001
From: Andy Teijelo <ateijelo@gmail.com>
Date: Sun, 3 Dec 2023 01:30:57 -0500
Subject: [PATCH] day 3 part 2

---
 src/main.rs | 59 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 25 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index a8710c1..e328a79 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,49 +1,50 @@
 use anyhow::Result;
 use fancy_regex::Regex;
-use std::io::stdin;
+use std::{collections::HashMap, io::stdin};
 
-fn is_dot(x: i32, y: i32, lines: &[&[u8]]) -> bool {
+fn is_gear(x: i32, y: i32, lines: &[&[u8]]) -> bool {
     if x < 0 {
-        return true;
+        return false;
     }
     if y < 0 {
-        return true;
+        return false;
     }
     if y as usize >= lines.len() {
-        return true;
+        return false;
     }
     let line = &lines[y as usize];
     if x as usize >= line.len() {
-        return true;
+        return false;
     }
-    if line[x as usize] == b'.' {
+    if line[x as usize] == b'*' {
         return true;
     }
     false
 }
 
-fn all_dots(x: i32, y: i32, len: i32, lines: &[&[u8]]) -> bool {
-    for cx in (x - 1)..=(x + len) {
-        if !is_dot(cx, y - 1, lines) {
-            return 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 cx in (x - 1)..=(x + len) {
-        if !is_dot(cx, y + 1, lines) {
-            return false;
+    for cy in (y - 1)..=y {
+        if is_gear(x + len, cy, lines) {
+            v.push((x + len, cy));
         }
     }
-    for cy in (y - 1)..=(y + 1) {
-        if !is_dot(x - 1, cy, lines) {
-            return false;
+    for cx in x..=(x + len) {
+        if is_gear(cx, y + 1, lines) {
+            v.push((cx, y + 1));
         }
     }
-    for cy in (y - 1)..=(y + 1) {
-        if !is_dot(x + len, cy, lines) {
-            return false;
+    for cy in y..=(y + 1) {
+        if is_gear(x - 1, cy, lines) {
+            v.push((x - 1, cy));
         }
     }
-    true
+    v
 }
 
 fn main() -> Result<()> {
@@ -53,23 +54,31 @@ fn main() -> Result<()> {
     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 (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()?;
-            println!("{lineno} {num} {} {}", num_match.start(), num_text.len());
-            if !all_dots(
+            let gears = find_gears(
                 num_match.start() as i32,
                 lineno as i32,
                 num_text.len() as i32,
                 &raw_lines,
-            ) {
-                sum += num;
+            );
+            for gear in gears {
+                let e = gear_map.entry(gear).or_default();
+                e.push(num);
             }
         }
     }
+    for v in gear_map.values() {
+        if v.len() == 2 {
+            sum += v.iter().product::<i32>();
+        }
+    }
 
     println!("{sum}");