From e112f44360971a2909409af513be8f4df46627e5 Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Wed, 2 Dec 2020 00:53:09 -0500
Subject: puzzle 2-2

---
 src/2020/2/mod.rs | 50 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 17 deletions(-)

diff --git a/src/2020/2/mod.rs b/src/2020/2/mod.rs
index 88d3f5b..71afd7a 100644
--- a/src/2020/2/mod.rs
+++ b/src/2020/2/mod.rs
@@ -3,8 +3,8 @@ use std::io::BufRead as _;
 
 struct Line {
     c: char,
-    min_times: usize,
-    max_times: usize,
+    n1: usize,
+    n2: usize,
     password: String,
 }
 
@@ -19,13 +19,13 @@ impl Line {
             .as_str()
             .parse()
             .context("invalid policy char")?;
-        let min_times = captures
+        let n1 = captures
             .get(1)
             .unwrap()
             .as_str()
             .parse()
             .context("invalid policy lower bound")?;
-        let max_times = captures
+        let n2 = captures
             .get(2)
             .unwrap()
             .as_str()
@@ -34,31 +34,47 @@ impl Line {
         let password = captures.get(4).unwrap().as_str().to_string();
         Ok(Self {
             c,
-            min_times,
-            max_times,
+            n1,
+            n2,
             password,
         })
     }
 
-    fn valid(&self) -> bool {
+    fn valid_part_1(&self) -> bool {
         let count = self.password.chars().filter(|c| *c == self.c).count();
-        count >= self.min_times && count <= self.max_times
+        count >= self.n1 && count <= self.n2
+    }
+
+    fn valid_part_2(&self) -> bool {
+        let valid = (self.password.chars().nth(self.n1 - 1) == Some(self.c))
+            ^ (self.password.chars().nth(self.n2 - 1) == Some(self.c));
+        println!(
+            "{}-{} {}: {} ({})",
+            self.n1, self.n2, self.c, self.password, valid,
+        );
+        valid
     }
 }
 
 pub fn part1() -> anyhow::Result<()> {
-    let f = std::fs::File::open("data/2.txt")
-        .context("couldn't find data file 2.txt")?;
-    let f = std::io::BufReader::new(f);
-    let lines = f
-        .lines()
-        .map(|l| Line::parse(&l.context("failed to read a line")?))
-        .collect::<anyhow::Result<Vec<Line>>>()?;
-    let count = lines.iter().filter(|l| l.valid()).count();
+    let lines = read_lines()?;
+    let count = lines.iter().filter(|l| l.valid_part_1()).count();
     println!("{}", count);
     Ok(())
 }
 
 pub fn part2() -> anyhow::Result<()> {
-    todo!()
+    let lines = read_lines()?;
+    let count = lines.iter().filter(|l| l.valid_part_2()).count();
+    println!("{}", count);
+    Ok(())
+}
+
+fn read_lines() -> anyhow::Result<Vec<Line>> {
+    let f = std::fs::File::open("data/2.txt")
+        .context("couldn't find data file 2.txt")?;
+    let f = std::io::BufReader::new(f);
+    f.lines()
+        .map(|l| Line::parse(&l.context("failed to read a line")?))
+        .collect()
 }
-- 
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