From 71fb3478c3a69dbbbe75548fd4d4fa3f7f166521 Mon Sep 17 00:00:00 2001
From: Alpha Chen <alpha.chen@gmail.com>
Date: Mon, 3 Dec 2018 20:43:34 -0800
Subject: [PATCH] [2018][rust][3.1]

---
 2018/rust/src/bin/day_03.rs | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/2018/rust/src/bin/day_03.rs b/2018/rust/src/bin/day_03.rs
index c636e37..23fda72 100644
--- a/2018/rust/src/bin/day_03.rs
+++ b/2018/rust/src/bin/day_03.rs
@@ -21,17 +21,24 @@ fn solve(input: &str) -> Result<String, Box<Error>> {
         .map(str::trim)
         .map(Claim::from_str)
         .collect::<Result<_, _>>()?;
-    let fabric = claims.iter().fold(HashMap::new(), |mut fabric, claim| {
+    let fabric = claims.iter().fold(HashMap::new(), |mut fabric: HashMap<(usize, usize), Vec<usize>>, claim| {
         for square_inch in claim.square_inches() {
             fabric
                 .entry(square_inch)
-                .and_modify(|count| *count += 1)
-                .or_insert(1);
+                .and_modify(|ids| ids.push(claim.id))
+                .or_insert(vec![claim.id]);
         }
         fabric
     });
-    let output = fabric.values().filter(|&&count| count > 1).count();
-    Ok(output.to_string())
+    let values: Vec<_> = fabric.values().collect();
+    let output = values
+        .iter()
+        .map(|ids| ids[0])
+        .filter(|id| !values.iter().any(|ids| ids.len() > 1 && ids.contains(id)))
+        .next()
+        .unwrap()
+        .to_string();
+    Ok(output)
 }
 
 #[test]
@@ -43,7 +50,7 @@ fn test_solve() {
     "
     .trim();
 
-    assert_eq!(&solve(input).unwrap(), "4");
+    assert_eq!(&solve(input).unwrap(), "3");
 }
 
 #[derive(Debug, PartialEq, Eq)]