summary refs log tree commit diff homepage
path: root/src
diff options
context:
space:
mode:
Diffstat (limited to 'src')
-rw-r--r--src/bin/day21.rs30
1 files changed, 27 insertions, 3 deletions
diff --git a/src/bin/day21.rs b/src/bin/day21.rs
index c9abb76..982bf8a 100644
--- a/src/bin/day21.rs
+++ b/src/bin/day21.rs
@@ -87,7 +87,7 @@ impl<'a> From<&'a str> for Operation {
     }
 }
 
-fn solve(password: &str, input: &str) -> String {
+fn solve1(password: &str, input: &str) -> String {
     let mut password = password.as_bytes().to_owned();
 
     for operation in input.lines().map(Operation::from) {
@@ -97,11 +97,35 @@ fn solve(password: &str, input: &str) -> String {
     String::from_utf8(password).unwrap()
 }
 
+fn solve2(scrambled: &str, input: &str) -> String {
+    let operations: Vec<_> = input.lines().map(Operation::from).collect();
+
+    let mut password = "abcdefgh".as_bytes().to_owned();
+    let len = password.len();
+
+    loop {
+        let k = (0..(len - 1)).rev().find(|&k| password[k] < password [k + 1]).unwrap();
+        let l = ((k + 1)..len).rev().find(|&l| password[k] < password[l]).unwrap();
+        password.swap(k, l);
+        password[(k + 1)..].reverse();
+
+        let mut candidate = password.clone();
+        for operation in &operations {
+            operation.apply(&mut candidate);
+        }
+
+        if candidate == scrambled.as_bytes() {
+            return String::from_utf8(password).unwrap();
+        }
+    }
+}
+
 fn main() {
     let mut input = String::new();
     io::stdin().read_to_string(&mut input).unwrap();
 
-    println!("Part 1: {}", solve("abcdefgh", &input));
+    println!("Part 1: {}", solve1("abcdefgh", &input));
+    println!("Part 2: {}", solve2("fbgdceah", &input));
 }
 
 #[test]
@@ -116,5 +140,5 @@ move position 3 to position 0
 rotate based on position of letter b
 rotate based on position of letter d
 ";
-    assert_eq!("decab", solve("abcde", input.trim()));
+    assert_eq!("decab", solve1("abcde", input.trim()));
 }
44e7c4fe69241beda1d0a086bc&follow=1'>Add capsicum note to READMEJune McEnroe 2019-11-10Filter extended-joinJune McEnroe 2019-11-10Expand client configuration documentation and list capabilitiesJune McEnroe 2019-11-10Request all supported caps from serverJune McEnroe 2019-11-10Filter ACCOUNT, AWAY, CHGHOST for incapable clientsJune McEnroe 2019-11-10Rename listen to localJune McEnroe 2019-11-09Remove extended-join and invite-notifyJune McEnroe The remaining caps only generate new commands which can easily be filtered out when sending to clients so will be in the first pass of support. extended-join is probably safe to pass through unaltered, just causing extraneous parameters on JOIN commands, but maybe not. invite-notify reuses the INVITE command where the invited user is not self. 2019-11-09Maintain stateCaps and offer them to clientsJune McEnroe 2019-11-09Parse capabilitiesJune McEnroe The list that I've defined are the ones that I expect to be able to enable probably without any clients breaking... And of course server-time which pounce implements itself. 2019-11-09Avoid the reserved _A names with BIT macroJune McEnroe 2019-11-09Define macro for bit flag enumsJune McEnroe 2019-11-08Check that password is hashedJune McEnroe 2019-11-08Avoid calling getopt_long again after it returns -1June McEnroe On GNU, calling getopt_long again will reset optind back to the first non-option argument, which would cause an infinite loop of reading the same configurtion file forever. 2019-11-08Only change AWAY status for registered clientsJune McEnroe Turns out I did eventually fix this, because I may want to implement "passive clients" for logging or notification stuff, which wouldn't affect AWAY status either. 2019-11-07Just write the example normallyJune McEnroe 2019-11-07Include path in readlinkat errorJune McEnroe 2019-11-07Call clientConsume before clientRecvJune McEnroe This might reduce the frequency of a client getting its own message back because it was behind in the ring when it sent it. 2019-11-06Use -l:filename in Linux.mkJune McEnroe 2019-11-06Fix compat.h for #defined strlcpyJune McEnroe 2019-11-06Allow unsetting LIBRESSL_PREFIXJune McEnroe 2019-11-06Document calico service configurationJune McEnroe 2019-11-06Document SASL EXTERNAL configuration in more detailJune McEnroe 2019-11-06Document pounce service configurationJune McEnroe 2019-11-06Mention Darwin and GNU/Linux in READMEJune McEnroe 2019-11-06Assume LibreSSL from brew on DarwinJune McEnroe 2019-11-06Remove -DNO_EXPLICIT_BZERO from Darwin.mkJune McEnroe 2019-11-06Don't install rc scripts or dirs on LinuxJune McEnroe