From 6be2bc197968f2a338720769c1986e08b72fbe33 Mon Sep 17 00:00:00 2001
From: Ivan Tham <pickfire@riseup.net>
Date: Wed, 3 Mar 2021 01:20:25 +0800
Subject: [PATCH] day5b find within possible values

---
 day5b/src/main.rs | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/day5b/src/main.rs b/day5b/src/main.rs
index c513b01..fa53997 100644
--- a/day5b/src/main.rs
+++ b/day5b/src/main.rs
@@ -5,21 +5,22 @@ use std::io::Read;
 fn main() {
     let mut input = String::new();
     io::stdin().read_to_string(&mut input).unwrap();
-    let passes: HashSet<u16> = input
+    let mut seats: Vec<_> = input
         .lines()
-        .map(|x| x.chars().rev().map(|y| match y {
-            'F' => 0,
-            'B' => 1,
-            'L' => 0,
-            'R' => 1,
-            _ => 0,
-        }).enumerate().fold(0, |acc, x| acc + (x.1 << x.0)))
+        .map(|l| {
+            l.bytes().fold(0, |a, b| {
+                a << 1 | if b == b'B' || b == b'R' { 1 } else { 0 }
+            })
+        })
         .collect();
-
-    for i in 0..(1 << 10) - 1 {
-        if passes.contains(&(i - 1)) && passes.contains(&(i + 1)) && !passes.contains(&i) {
-            println!("{}", i);
-            break;
-        }
-    }
+    seats.sort();
+ 
+    println!(
+        "{}",
+        seats
+            .windows(2)
+            .find(|s| s[1] - s[0] == 2)
+            .map(|s| s[0] + 1)
+            .unwrap()
+    );
 }