From 8fe3e93bd619ab3d2564f127b33cb2cd97087b03 Mon Sep 17 00:00:00 2001
From: Tyler Hallada <tyler@hallada.net>
Date: Fri, 14 Dec 2018 22:39:40 -0500
Subject: [PATCH] Day 1 part 2

I didn't realize there was a part two before.
---
 inputs/1_test_part2.txt   |  5 ++++
 inputs/1_test_part2_2.txt |  5 ++++
 inputs/1_test_part2_3.txt |  5 ++++
 src/day1.rs               | 59 ++++++++++++++++++++++++++++++++++++++-
 src/main.rs               |  3 +-
 5 files changed, 75 insertions(+), 2 deletions(-)
 create mode 100644 inputs/1_test_part2.txt
 create mode 100644 inputs/1_test_part2_2.txt
 create mode 100644 inputs/1_test_part2_3.txt

diff --git a/inputs/1_test_part2.txt b/inputs/1_test_part2.txt
new file mode 100644
index 0000000..78cd296
--- /dev/null
+++ b/inputs/1_test_part2.txt
@@ -0,0 +1,5 @@
++7
++7
+-2
+-7
+-4
diff --git a/inputs/1_test_part2_2.txt b/inputs/1_test_part2_2.txt
new file mode 100644
index 0000000..bdee386
--- /dev/null
+++ b/inputs/1_test_part2_2.txt
@@ -0,0 +1,5 @@
++3
++3
++4
+-2
+-4
diff --git a/inputs/1_test_part2_3.txt b/inputs/1_test_part2_3.txt
new file mode 100644
index 0000000..f6f3cf5
--- /dev/null
+++ b/inputs/1_test_part2_3.txt
@@ -0,0 +1,5 @@
+-6
++3
++8
++5
+-6
diff --git a/src/day1.rs b/src/day1.rs
index 7fcaaef..ddb86d9 100644
--- a/src/day1.rs
+++ b/src/day1.rs
@@ -1,13 +1,19 @@
 use std::error::Error;
 use std::fs::File;
 use std::io::{BufRead, BufReader};
+use std::collections::HashSet;
 
 const INPUT: &str = "inputs/1.txt";
+const LOOP_LIMIT: u16 = 1000;
 
-pub fn solve() -> Result<i32, Box<Error>> {
+pub fn solve_part1() -> Result<i32, Box<Error>> {
     calculate_resulting_frequency(INPUT)
 }
 
+pub fn solve_part2() -> Result<Option<i32>, Box<Error>> {
+    find_repeating_frequency(INPUT)
+}
+
 fn calculate_resulting_frequency(filename: &str) -> Result<i32, Box<Error>> {
     let mut freq: i32 = 0;
     let file = File::open(filename)?;
@@ -18,14 +24,65 @@ fn calculate_resulting_frequency(filename: &str) -> Result<i32, Box<Error>> {
     Ok(freq)
 }
 
+fn find_repeating_frequency(filename: &str) -> Result<Option<i32>, Box<Error>> {
+    let freqs = read_frequencies(filename)?;
+    let mut result_freqs = HashSet::new();
+    let mut freq: i32 = 0;
+    let mut loop_count = 0;
+    while loop_count < LOOP_LIMIT {
+        for adjustment in &freqs {
+            freq += adjustment;
+            if result_freqs.contains(&freq) {
+                return Ok(Some(freq))
+            } else {
+                result_freqs.insert(freq);
+            }
+        }
+        loop_count += 1
+    }
+    Ok(None)
+}
+
+fn read_frequencies(filename: &str) -> Result<Vec<i32>, Box<Error>> {
+    let mut freqs: Vec<i32> = Vec::new();
+    let file = File::open(filename)?;
+    for line in BufReader::new(file).lines() {
+        freqs.push(line?.parse()?);
+    }
+    Ok(freqs)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
     const TEST_INPUT: &str = "inputs/1_test.txt";
+    const TEST_INPUT_PART_2: &str = "inputs/1_test_part2.txt";
+    const TEST_INPUT_PART_2_2: &str = "inputs/1_test_part2_2.txt";
+    const TEST_INPUT_PART_2_3: &str = "inputs/1_test_part2_3.txt";
 
     #[test]
     fn finds_resulting_frequency() {
         assert_eq!(calculate_resulting_frequency(TEST_INPUT).unwrap(), 3);
     }
+
+    #[test]
+    fn finds_repeating_frequency() {
+        assert_eq!(find_repeating_frequency(TEST_INPUT_PART_2).unwrap().unwrap(), 14);
+    }
+
+    #[test]
+    fn finds_repeating_frequency_2() {
+        assert_eq!(find_repeating_frequency(TEST_INPUT_PART_2_2).unwrap().unwrap(), 10);
+    }
+
+    #[test]
+    fn finds_repeating_frequency_3() {
+        assert_eq!(find_repeating_frequency(TEST_INPUT_PART_2_3).unwrap().unwrap(), 5);
+    }
+
+    #[test]
+    fn reads_frequencies_file() {
+        assert_eq!(read_frequencies(TEST_INPUT).unwrap(), vec![5, -5, 3]);
+    }
 }
diff --git a/src/main.rs b/src/main.rs
index 2a2d172..a807a0f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,7 +3,8 @@ mod day2;
 
 fn main() {
     println!("Day 1:");
-    println!("{}", day1::solve().unwrap());
+    println!("{}", day1::solve_part1().unwrap());
+    println!("{}", day1::solve_part2().unwrap().unwrap());
     println!("Day 2:");
     println!("{}", day2::solve_part1().unwrap());
     println!("{}", day2::solve_part2().unwrap().unwrap());