[Day01] Part 2

Author: hindenbug

day01/src/main.rs

@@ -1,6 +1,7 @@
 use std::io;
 use std::io::{Read};
 use std::fs::File;
+use std::collections::HashSet;
 
 fn main() -> io::Result<()> {
     let mut input = String::new();
@@ -9,31 +10,70 @@ fn main() -> io::Result<()> {
     f.read_to_string(&mut input)?;
 
     let p1 = part_one(&input)?;
-    println!("Part 1: {}", p1);
+    println!("Part 1: {:?}", p1);
+
+    let p2 = part_two(&input)?;
+    println!("Part 2: {:?}", p2);
 
     Ok(())
 }
 
 fn part_one(input: &str) -> io::Result<(i32)> {
     let res = input
         .lines()
-        .map(|l| l.parse::<i32>().unwrap()).sum();
+        .map(|l| l.parse::<i32>().unwrap())
+        .sum();
 
     Ok(res)
 }
 
+fn part_two(input: &str) -> io::Result<(i32)> {
+    let mut freq = 0;
+    let mut seen_freqs: HashSet<i32> = HashSet::new();
+    seen_freqs.insert(freq);
+
+    let freq_changes = input
+        .lines()
+        .map(|l| l.parse::<i32>().unwrap())
+        .cycle();
+
+    for change in freq_changes {
+        freq += change;
+        if seen_freqs.contains(&freq) {
+            break;
+        }
+        seen_freqs.insert(freq);
+    }
+
+    Ok(freq)
+}
+
+
 #[cfg(test)]
 mod tests {
-  use super::*;
-
-  #[test]
-  fn test_part_one() {
-    let input1 = "+1\n+1\n+1";
-    let input2 = "+1\n+1\n-2";
-    let input3 = "-1\n-2\n-3";
-
-    assert_eq!(part_one(&input1).unwrap(), 3);
-    assert_eq!(part_one(&input2).unwrap(), 0);
-    assert_eq!(part_one(&input3).unwrap(), -6);
-  }
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let input1 = "+1\n+1\n+1";
+        let input2 = "+1\n+1\n-2";
+        let input3 = "-1\n-2\n-3";
+
+        assert_eq!(part_one(&input1).unwrap(), 3);
+        assert_eq!(part_one(&input2).unwrap(), 0);
+        assert_eq!(part_one(&input3).unwrap(), -6);
+    }
+
+    #[test]
+    fn test_part_two() {
+        let input1 = "+1\n-1";
+        let input2 = "+3\n+3\n+4\n-2\n-4";
+        let input3 = "-6\n+3\n+8\n+5\n-6";
+        let input4 = "+7\n+7\n-2\n-7\n-4";
+
+        assert_eq!(part_two(&input1).unwrap(), 0);
+        assert_eq!(part_two(&input2).unwrap(), 10);
+        assert_eq!(part_two(&input3).unwrap(), 5);
+        assert_eq!(part_two(&input4).unwrap(), 14);
+    }
 }