diff --git a/2018/day4/Cargo.lock b/2018/day4/Cargo.lock
new file mode 100644
index 0000000..58d2fe6
--- /dev/null
+++ b/2018/day4/Cargo.lock
@@ -0,0 +1,96 @@
+[[package]]
+name = "aho-corasick"
+version = "0.6.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "memchr 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "cfg-if"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "day4"
+version = "0.1.0"
+dependencies = [
+ "lazy_static 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "lazy_static"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
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+name = "libc"
+version = "0.2.44"
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+
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+name = "memchr"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.44 (registry+https://github.com/rust-lang/crates.io-index)",
+ "version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
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+]
+
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+]
+
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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diff --git a/2018/day4/Cargo.toml b/2018/day4/Cargo.toml
index f392a82..c8bcb3e 100644
--- a/2018/day4/Cargo.toml
+++ b/2018/day4/Cargo.toml
@@ -4,3 +4,5 @@ version = "0.1.0"
 authors = ["Andrew Coleman <penguincoder@gmail.com>"]
 
 [dependencies]
+regex = "1"
+lazy_static = "1"
diff --git a/2018/day4/src/main.rs b/2018/day4/src/main.rs
index e7a11a9..0561093 100644
--- a/2018/day4/src/main.rs
+++ b/2018/day4/src/main.rs
@@ -1,3 +1,123 @@
-fn main() {
-    println!("Hello, world!");
+#[macro_use]
+extern crate lazy_static;
+extern crate regex;
+
+use regex::Regex;
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+use std::iter::Iterator;
+
+type Day4Map = HashMap<u16, [u16; 60]>;
+
+fn calc_minutes_from_lines(lines: &mut Vec<String>, map: &mut Day4Map, gid: u16, start: u16) {
+    lazy_static! {
+        static ref GUARD_RE: Regex =
+            Regex::new(r"^\[\d{4}-\d{2}-\d{2} \d{2}:\d{2}\] Guard #(\d+) begins shift$").unwrap();
+        static ref ASLEEP_RE: Regex =
+            Regex::new(r"^\[\d{4}-\d{2}-\d{2} \d{2}:(\d{2})\] falls asleep$").unwrap();
+        static ref AWAKE_RE: Regex =
+            Regex::new(r"^\[\d{4}-\d{2}-\d{2} \d{2}:(\d{2})\] wakes up$").unwrap();
+    }
+
+    let line = lines.remove(0);
+    let line = line.as_str();
+    let guard_id = if GUARD_RE.is_match(line) {
+        let caps = GUARD_RE.captures(line).unwrap();
+        caps[1].parse::<u16>().unwrap()
+    } else {
+        gid
+    };
+
+    let start_minute = if ASLEEP_RE.is_match(line) {
+        let caps = ASLEEP_RE.captures(line).unwrap();
+        caps[1].parse::<u16>().unwrap()
+    } else {
+        start
+    };
+
+    if AWAKE_RE.is_match(line) {
+        let caps = AWAKE_RE.captures(line).unwrap();
+        let end_minute = caps[1].parse::<u16>().unwrap();
+        map.entry(guard_id)
+            .and_modify(|e| {
+                for minute in (start_minute..end_minute).into_iter() {
+                    e[usize::from(minute)] += 1;
+                }
+            })
+            .or_insert([0u16; 60]);
+    };
+
+    if lines.is_empty() {
+        return;
+    } else {
+        calc_minutes_from_lines(lines, map, guard_id, start_minute)
+    }
+}
+
+fn get_max_from_map(map: &mut Day4Map) -> HashMap<u16, u16> {
+    let mut count_map: HashMap<u16, u16> = HashMap::new();
+    let mut max_gid = 0;
+    let mut max_count = 0;
+    let mut max_minute = 0;
+    let mut most_max_gid = 0;
+    let mut most_max_minute = 0;
+    let mut most_max_minute_index = 0;
+
+    for (key, value) in map {
+        let sum = value.into_iter().sum();
+        if sum > max_count {
+            max_gid = *key;
+            max_count = sum;
+            let mut cur_max_min = 0;
+            for i in 0..value.len() {
+                if value[i] > cur_max_min {
+                    cur_max_min = value[i];
+                    max_minute = i as u16;
+                }
+            }
+        }
+
+        for i in 0..value.len() {
+            if value[i] > most_max_minute {
+                most_max_minute = value[i];
+                most_max_minute_index = i as u16;
+                most_max_gid = *key;
+            }
+        }
+
+        count_map.insert(*key, sum);
+    }
+    println!(
+        "max guard id is {} sum {}, max minute of {} with val of {}",
+        max_gid,
+        max_count,
+        max_minute,
+        max_gid * max_minute
+    );
+    println!(
+        "guard {} most asleep on a single minute {} with a count of {} is {}",
+        most_max_gid,
+        most_max_minute_index,
+        most_max_minute,
+        most_max_gid * most_max_minute_index
+    );
+    count_map
+}
+
+fn main() {
+    let mut lines: Vec<String> = BufReader::new(File::open("sorted-input").unwrap())
+        .lines()
+        .map(|line| line.unwrap())
+        .collect();
+    let mut map = Day4Map::new();
+    calc_minutes_from_lines(&mut lines, &mut map, 0, 0);
+    /*for (key, value) in &map {
+        print!("{}: ", key);
+        for r in value.iter() {
+            print!("{} ", r);
+        }
+        println!();
+    }*/
+    get_max_from_map(&mut map);
 }