Day 14

1 files changed, 60 insertions, 0 deletions

diff --git a/src/bin/day14.rs b/src/bin/day14.rs
new file mode 100644
index 0000000..b22e88d
--- /dev/null
+++ b/src/bin/day14.rs
@@ -0,0 +1,60 @@
+extern crate crypto;
+
+use std::collections::VecDeque;
+use std::io::{self, Read};
+use std::iter;
+
+use crypto::digest::Digest;
+use crypto::md5::Md5;
+
+fn md5(salt: &str, index: u32) -> String {
+    let mut md5 = Md5::new();
+    md5.input_str(salt);
+    md5.input_str(&index.to_string());
+    md5.result_str()
+}
+
+fn solve(salt: &str) -> u32 {
+    let mut hashes = VecDeque::new();
+    for i in 0..1001 {
+        hashes.push_back(md5(salt, i));
+    }
+
+    let mut keys = 0;
+    let mut index = 0;
+    while let Some(hash) = hashes.pop_front() {
+        let triple = hash.as_bytes()
+            .windows(3)
+            .filter(|w| w[0] == w[1] && w[1] == w[2])
+            .map(|w| w[0])
+            .next();
+
+        if let Some(ch) = triple {
+            let quintuple: String = iter::repeat(ch as char).take(5).collect();
+            if hashes.iter().any(|hash| hash.contains(&quintuple)) {
+                keys += 1;
+                if keys == 64 {
+                    return index;
+                }
+            }
+        }
+
+        index += 1;
+        hashes.push_back(md5(salt, 1000 + index));
+    }
+
+    unreachable!()
+}
+
+fn main() {
+    let mut input = String::new();
+    io::stdin().read_to_string(&mut input).unwrap();
+
+    println!("Part 1: {}", solve(input.trim()));
+}
+
+#[test]
+#[ignore]
+fn part1() {
+    assert_eq!(22728, solve("abc"));
+}