From e1b0047d2e8e148d021eb4678e20dcac11533baf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thorben=20G=C3=BCnther?= <admin@xenrox.net>
Date: Wed, 7 Apr 2021 23:49:40 +0200
Subject: [PATCH] Solve day 2 part 2

---
 src/days/day02.rs | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/days/day02.rs b/src/days/day02.rs
index ef63291..a03d4d0 100644
--- a/src/days/day02.rs
+++ b/src/days/day02.rs
@@ -28,7 +28,7 @@ fn parse_contents(contents: String) -> Vec<Policy> {
     policies
 }
 
-fn count_valid_passwords(policies: &Vec<Policy>) -> i32 {
+fn count_valid_passwords1(policies: &Vec<Policy>) -> i32 {
     let mut count_valid = 0;
     for policy in policies {
         let count = policy.password.matches(policy.letter).count();
@@ -39,12 +39,25 @@ fn count_valid_passwords(policies: &Vec<Policy>) -> i32 {
     count_valid
 }
 
+fn count_valid_passwords2(policies: &Vec<Policy>) -> i32 {
+    let mut count_valid = 0;
+    for policy in policies {
+        let first = policy.password.chars().nth(policy.min - 1).unwrap();
+        let second = policy.password.chars().nth(policy.max - 1).unwrap();
+        if (first == policy.letter) ^ (second == policy.letter) {
+            count_valid += 1;
+        }
+    }
+    count_valid
+}
+
 pub fn get_solution() {
     let contents = fs::read_to_string("data/day02.dat").expect("Could not read data");
     let policies = parse_contents(contents);
-    let count_valid = count_valid_passwords(&policies);
+    let count_valid1 = count_valid_passwords1(&policies);
+    let count_valid2 = count_valid_passwords2(&policies);
 
-    println!("Day 2, part 1: {}", count_valid);
+    println!("Day 2, part 1: {}, part 2: {}", count_valid1, count_valid2);
 }
 
 #[cfg(test)]
@@ -58,6 +71,16 @@ mod tests {
             1-3 b: cdefg
             2-9 c: ccccccccc",
         );
-        assert_eq!(count_valid_passwords(&parse_contents(contents)), 2);
+        assert_eq!(count_valid_passwords1(&parse_contents(contents)), 2);
+    }
+
+    #[test]
+    fn part2() {
+        let contents = String::from(
+            "1-3 a: abcde
+            1-3 b: cdefg
+            2-9 c: ccccccccc",
+        );
+        assert_eq!(count_valid_passwords2(&parse_contents(contents)), 1);
     }
 }
-- 
2.44.0