diff --git a/Cargo.lock b/Cargo.lock
index 87d1537..3b949fc 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -199,6 +199,14 @@ version = "0.1.0"
 name = "day_13"
 version = "0.1.0"
 
+[[package]]
+name = "day_14"
+version = "0.1.0"
+dependencies = [
+ "criterion",
+ "day_10",
+]
+
 [[package]]
 name = "day_15"
 version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 6ae2742..3cc1112 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,6 +13,7 @@ members = [
     "day_11",
     "day_12",
     "day_13",
+    "day_14",
     "day_15",
     "day_16",
     "day_17",
diff --git a/day_10/src/lib.rs b/day_10/src/lib.rs
index 5dc7093..16367bd 100644
--- a/day_10/src/lib.rs
+++ b/day_10/src/lib.rs
@@ -69,28 +69,31 @@ pub mod day_10 {
         }
     }
 
-    pub fn knot_hash_unsalted(bytes: &[u8]) -> String {
+    pub fn knot_hash_unsalted(bytes: &[u8]) -> Vec<u8> {
         let mut state = new_state(256);
         for _ in 0..64 {
             execute_round(&mut state, &bytes);
         }
-        let dense = densify(&state.v);
-        let mut answer = vec![0u8; 2 * dense.len()];
-        for (i, b) in dense.iter().enumerate() {
+        densify(&state.v)
+    }
+
+    pub fn knot_hash(bytes: &[u8]) -> Vec<u8> {
+        let mut copy: Vec<u8> = bytes.to_vec();
+        copy.extend(vec![17, 31, 73, 47, 23]);
+        knot_hash_unsalted(&copy)
+    }
+
+    pub fn to_hex_str(bytes: &[u8]) -> String {
+        let mut answer = vec![0u8; 2 * bytes.len()];
+        for (i, b) in bytes.iter().enumerate() {
             answer[2 * i] = to_hex(b / 16);
             answer[2 * i + 1] = to_hex(b % 16);
         }
         String::from_utf8(answer).unwrap()
     }
 
-    pub fn knot_hash(bytes: &[u8]) -> String {
-        let mut copy: Vec<u8> = bytes.to_vec();
-        copy.extend(vec![17, 31, 73, 47, 23]);
-        knot_hash_unsalted(&copy)
-    }
-
     pub fn part_2(input: &[u8]) -> String {
-        knot_hash(input)
+        to_hex_str(&knot_hash(input))
     }
 }
 
@@ -109,17 +112,20 @@ mod tests {
 
     #[test]
     fn part2_known() {
-        assert_eq!(knot_hash("".as_bytes()), "a2582a3a0e66e6e86e3812dcb672a272");
         assert_eq!(
-            knot_hash("AoC 2017".as_bytes()),
+            to_hex_str(&knot_hash("".as_bytes())),
+            "a2582a3a0e66e6e86e3812dcb672a272"
+        );
+        assert_eq!(
+            to_hex_str(&knot_hash("AoC 2017".as_bytes())),
             "33efeb34ea91902bb2f59c9920caa6cd"
         );
         assert_eq!(
-            knot_hash("1,2,3".as_bytes()),
+            to_hex_str(&knot_hash("1,2,3".as_bytes())),
             "3efbe78a8d82f29979031a4aa0b16a9d"
         );
         assert_eq!(
-            knot_hash("1,2,4".as_bytes()),
+            to_hex_str(&knot_hash("1,2,4".as_bytes())),
             "63960835bcdc130f0b66d7ff4f6a5a8e"
         );
     }
diff --git a/day_14/Cargo.toml b/day_14/Cargo.toml
new file mode 100644
index 0000000..907f95c
--- /dev/null
+++ b/day_14/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "day_14"
+version = "0.1.0"
+authors = ["Smaug123 <patrick+github@patrickstevens.co.uk>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+day_10 =  { path = "../day_10" }
+
+[dev-dependencies]
+criterion = "0.3"
+
+[[bench]]
+name = "day_14"
+harness = false
diff --git a/day_14/benches/day_14.rs b/day_14/benches/day_14.rs
new file mode 100644
index 0000000..fd9da03
--- /dev/null
+++ b/day_14/benches/day_14.rs
@@ -0,0 +1,24 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+use day_14::day_14::{input, part_1, part_1_longhand, part_2};
+
+fn criterion_benchmark(c: &mut Criterion) {
+    let input = input();
+    c.bench_function("day 14 part 1", |b| {
+        b.iter(|| {
+            part_1(&input);
+        })
+    });
+    c.bench_function("day 14 part 1 longhand", |b| {
+        b.iter(|| {
+            part_1_longhand(&input);
+        })
+    });
+    c.bench_function("day 14 part 2", |b| {
+        b.iter(|| {
+            part_2(&input);
+        })
+    });
+}
+
+criterion_group!(benches, criterion_benchmark);
+criterion_main!(benches);
diff --git a/day_14/input.txt b/day_14/input.txt
new file mode 100644
index 0000000..f2fdb36
--- /dev/null
+++ b/day_14/input.txt
@@ -0,0 +1 @@
+ffayrhll
diff --git a/day_14/src/lib.rs b/day_14/src/lib.rs
new file mode 100644
index 0000000..29070db
--- /dev/null
+++ b/day_14/src/lib.rs
@@ -0,0 +1,207 @@
+pub mod day_14 {
+
+    use day_10::day_10::knot_hash;
+
+    pub fn input() -> &'static str {
+        include_str!("../input.txt").trim()
+    }
+
+    fn count_ones(i: u8) -> u8 {
+        let mut i = i;
+        let mut ans = 0;
+        while i > 0 {
+            if i % 2 == 1 {
+                ans += 1;
+            }
+            i /= 2;
+        }
+        ans
+    }
+
+    pub fn part_1_longhand(key: &str) -> u32 {
+        let mut buffer: Vec<u8> = key.chars().map(|i| i as u8).collect();
+        buffer.extend(&[b'-', b'0']);
+        let len = buffer.len();
+
+        let mut count = 0u32;
+
+        for i in 0u8..=9 {
+            buffer[len - 1] = i + b'0';
+            let hash = knot_hash(&buffer);
+            count += hash
+                .iter()
+                .cloned()
+                .map(|i| count_ones(i) as u32)
+                .sum::<u32>();
+        }
+
+        buffer.push(0);
+        for i in 1u8..=9 {
+            buffer[len - 1] = i + b'0';
+            for j in 0u8..=9 {
+                buffer[len] = j + b'0';
+                count += knot_hash(&buffer)
+                    .iter()
+                    .cloned()
+                    .map(|i| count_ones(i) as u32)
+                    .sum::<u32>();
+            }
+        }
+
+        buffer.push(0);
+        buffer[len - 1] = b'1';
+        for i in 0u8..=2 {
+            buffer[len] = i + b'0';
+            for j in 0u8..=(if i == 2 { 7 } else { 9 }) {
+                buffer[len + 1] = j + b'0';
+                count += knot_hash(&buffer)
+                    .iter()
+                    .cloned()
+                    .map(|i| count_ones(i) as u32)
+                    .sum::<u32>();
+            }
+        }
+
+        count
+    }
+
+    fn value_at<T>(i: &[T], width: usize, row: usize, col: usize) -> &T {
+        &i[row * width + col]
+    }
+
+    fn set_value_at<T>(i: &mut [T], width: usize, row: usize, col: usize, value: T) {
+        i[row * width + col] = value;
+    }
+
+    fn flood_fill(i: &mut [u32], width: usize, value: u32, row: usize, col: usize) {
+        let current = *value_at(i, width, row, col);
+        if current != 1 {
+            return;
+        }
+        set_value_at(i, width, row, col, value);
+        if row < (i.len() / width) - 1 {
+            flood_fill(i, width, value, row + 1, col);
+        }
+        if row > 0 {
+            flood_fill(i, width, value, row - 1, col);
+        }
+        if col > 0 {
+            flood_fill(i, width, value, row, col - 1);
+        }
+        if col < width - 1 {
+            flood_fill(i, width, value, row, col + 1);
+        }
+    }
+
+    fn count_contiguous(mut i: Vec<u32>, width: usize) -> u32 {
+        // 0 means empty, 1 means "full and not assigned a group".
+        let height = i.len() / width;
+        let mut next_group_number = 2;
+        for row in 0..height {
+            for col in 0..width {
+                if *value_at(&i, width, row, col) == 1 {
+                    flood_fill(&mut i, width, next_group_number, row, col);
+                    next_group_number += 1;
+                }
+            }
+        }
+        next_group_number - 2
+    }
+
+    pub(crate) fn render_vec(key: &str) -> Vec<u32> {
+        let mut output: Vec<u32> = vec![0; 128 * 128];
+        let mut buffer: Vec<u8> = key.chars().map(|i| i as u8).collect();
+        buffer.extend(&[b'-', b'0']);
+        let len = buffer.len();
+
+        let mut row = 0;
+
+        for i in 0u8..=9 {
+            buffer[len - 1] = i + b'0';
+            let hash = knot_hash(&buffer);
+            let mut col = 0;
+            for byte in hash {
+                let mut byte = byte;
+                for i in (0..8).rev() {
+                    set_value_at(&mut output, 128, row, col + i, (byte % 2) as u32);
+                    byte /= 2;
+                }
+                col += 8;
+            }
+            row += 1;
+        }
+
+        buffer.push(0);
+        for i in 1u8..=9 {
+            buffer[len - 1] = i + b'0';
+            for j in 0u8..=9 {
+                buffer[len] = j + b'0';
+                let hash = knot_hash(&buffer);
+                let mut col = 0;
+                for byte in hash {
+                    let mut byte = byte;
+                    for i in (0..8).rev() {
+                        set_value_at(&mut output, 128, row, col + i, (byte % 2) as u32);
+                        byte /= 2;
+                    }
+                    col += 8;
+                }
+                row += 1;
+            }
+        }
+
+        buffer.push(0);
+        buffer[len - 1] = b'1';
+        for i in 0u8..=2 {
+            buffer[len] = i + b'0';
+            for j in 0u8..=(if i == 2 { 7 } else { 9 }) {
+                buffer[len + 1] = j + b'0';
+                let hash = knot_hash(&buffer);
+                let mut col = 0;
+                for byte in hash {
+                    let mut byte = byte;
+                    for i in (0..8).rev() {
+                        set_value_at(&mut output, 128, row, col + i, (byte % 2) as u32);
+                        byte /= 2;
+                    }
+                    col += 8;
+                }
+                row += 1;
+            }
+        }
+
+        output
+    }
+
+    pub fn part_1(key: &str) -> usize {
+        render_vec(key).iter().cloned().filter(|i| *i == 1).count()
+    }
+
+    pub fn part_2(key: &str) -> u32 {
+        count_contiguous(render_vec(key), 128)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::day_14::*;
+
+    #[test]
+    fn part1_known() {
+        assert_eq!(part_1(&"flqrgnkx"), 8108);
+        assert_eq!(part_1_longhand(&"flqrgnkx"), 8108);
+    }
+
+    #[test]
+    fn part2_known() {
+        assert_eq!(part_2(&"flqrgnkx"), 1242);
+    }
+
+    #[test]
+    fn test_day_14() {
+        let input = input();
+        assert_eq!(part_1(input), 8190);
+        assert_eq!(part_1_longhand(input), 8190);
+        assert_eq!(part_2(&input), 1134);
+    }
+}
diff --git a/day_14/src/main.rs b/day_14/src/main.rs
new file mode 100644
index 0000000..7172ed1
--- /dev/null
+++ b/day_14/src/main.rs
@@ -0,0 +1,7 @@
+use day_14::day_14;
+
+fn main() {
+    let input = day_14::input();
+    println!("part 1 => {}", day_14::part_1(&input));
+    println!("part 2 => {}", day_14::part_2(&input));
+}