From 3f74dcb73e7d1aa17790784616e23a1ea4ee6886 Mon Sep 17 00:00:00 2001
From: Tyler Hallada <tyler@hallada.net>
Date: Mon, 17 Dec 2018 23:34:54 -0500
Subject: [PATCH] Day 4 part 2

It passes the tests but the real solution is incorrect :(
---
 src/day4.rs | 25 +++++++++++++++++++++++++
 src/main.rs |  1 +
 2 files changed, 26 insertions(+)

diff --git a/src/day4.rs b/src/day4.rs
index 82f998a..c25536f 100644
--- a/src/day4.rs
+++ b/src/day4.rs
@@ -65,6 +65,10 @@ pub fn solve_part1() -> Result<u32, Box<Error>> {
     Ok(get_part1(INPUT)?)
 }
 
+pub fn solve_part2() -> Result<u32, Box<Error>> {
+    Ok(get_part2(INPUT)?)
+}
+
 fn get_part1(filename: &str) -> Result<u32, Box<Error>> {
     let records = read_records(filename)?;
     let minutes_asleep = minutes_asleep_per_guard(records);
@@ -73,6 +77,22 @@ fn get_part1(filename: &str) -> Result<u32, Box<Error>> {
     Ok(sleepiest_guard.0 * sleepiest_minute)
 }
 
+fn get_part2(filename: &str) -> Result<u32, Box<Error>> {
+    let records = read_records(filename)?;
+    let minutes_asleep = minutes_asleep_per_guard(records);
+    let all_mins: Vec<u32> = minutes_asleep
+        .values()
+        .flat_map(|mins| mins.iter())
+        .cloned()
+        .collect();
+    let sleepiest_minute = mode(&all_mins[..]);
+    let sleepiest_guard = minutes_asleep
+        .iter()
+        .max_by_key(|(_, mins)| mins.into_iter().filter(|min| **min == sleepiest_minute).count())
+        .unwrap();
+    Ok(sleepiest_guard.0 * sleepiest_minute)
+}
+
 fn mode(numbers: &[u32]) -> u32 {
     let mut occurences = HashMap::new();
     for &value in numbers {
@@ -283,4 +303,9 @@ mod tests {
     fn solves_part1() {
         assert_eq!(get_part1(TEST_INPUT).unwrap(), 240);
     }
+
+    #[test]
+    fn solves_part2() {
+        assert_eq!(get_part2(TEST_INPUT).unwrap(), 4455);
+    }
 }
diff --git a/src/main.rs b/src/main.rs
index 43eba14..3694610 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -15,4 +15,5 @@ fn main() {
     println!("{}", day3::solve_part2().unwrap().unwrap());
     println!("Day 4:");
     println!("{}", day4::solve_part1().unwrap());
+    println!("{}", day4::solve_part2().unwrap());
 }