1 files changed, 84 insertions, 0 deletions
diff --git a/2016/aoc14/src/main.rs b/2016/aoc14/src/main.rs
new file mode 100644
index 0000000..d9410ce
--- /dev/null
+++ b/2016/aoc14/src/main.rs
@@ -0,0 +1,84 @@
+extern crate md5;
+
+use std::collections::HashMap;
+
+fn main() {
+//    let input = "abc";
+    let input = "yjdafjpo";
+    let mut index = 0;
+    let mut results_found = 0;
+
+    let mut hash_memo = HashMap::new();
+    while results_found < 64 {
+        let hash = stretched_hash(format!("{}{}", input, index), &mut hash_memo);
+        
+        let threes = find_concurrent_symbols(&hash, 3, true);
+        if threes.len() > 0 {
+//            println!("Found three at {} -> {}", index, hash);
+            for i in 1..1001 {
+                let hash = stretched_hash(format!("{}{}", input, index+i), &mut hash_memo);
+                let fives = find_concurrent_symbols(&hash, 5, false);
+                if fives.iter().any(|c| threes.contains(c)) {
+                    results_found += 1;
+//                    println!("Five found at {} -> {}", index+i, hash);
+                    println!("Found hash {} at index {}", results_found, index);
+                    break;
+                }
+            }
+        }
+        index += 1;
+    }
+    
+}
+
+fn find_concurrent_symbols(hash: &String, count: u8, exit_early: bool) -> Vec<char> {
+    let mut last_symbol = None;
+    let mut last_symbol_run = 0;
+    let mut matches = Vec::new();
+    for c in hash.chars() {
+        let symbol_matches = match last_symbol {
+            Some(s) => s == c,
+            None => false
+        };
+
+        if symbol_matches {
+            last_symbol_run += 1;
+            if last_symbol_run >= count && !matches.contains(&c) {
+                matches.push(c);
+                if exit_early {
+                    break;
+                }
+            }
+        } else {
+            last_symbol = Some(c);
+            last_symbol_run = 1;
+        }
+    }
+
+    matches
+}
+
+fn hash_to_string(hash: &[u8; 16]) -> String {
+    let mut result = String::with_capacity(32);
+    
+    for &byte in hash.iter() {
+        result.push_str(format!("{:02x}", byte).as_ref());
+    }
+    result
+}
+
+fn stretched_hash(input: String, memo: &mut HashMap<String, String>) -> String {
+    memo.entry(input.clone()).or_insert_with(|| {
+        let mut result = input;
+        for _ in 0..2017 {
+            result = string_hash(result);
+        }
+        result
+    }).clone()
+}
+
+fn string_hash(input: String) -> String {
+    let bytes_to_hash = input.into_bytes();
+    let hash = md5::compute(bytes_to_hash.as_slice());
+    hash_to_string(&hash)
+}