diff --git a/src/bin/11.rs b/src/bin/11.rs
new file mode 100644
index 000000000..ad0b884
--- /dev/null
+++ b/src/bin/11.rs
@@ -0,0 +1,117 @@
+use aoc::helpers::ASCII_LOWERCASE;
+use itertools::Itertools;
+
+fn allowed_password(password: &str) -> bool {
+    if password
+        .chars()
+        .filter(|x| vec!['i', 'o', 'l'].contains(x))
+        .count()
+        > 0
+    {
+        return false;
+    }
+
+    if password
+        .chars()
+        .tuple_windows()
+        .map(|(a, b, c)| ASCII_LOWERCASE.contains(&format!("{}{}{}", a, b, c)))
+        .filter(|&y| y)
+        .count()
+        == 0
+    {
+        return false;
+    }
+
+    if ASCII_LOWERCASE
+        .chars()
+        .map(|a| password.contains(&format!("{}{}", a, a)))
+        .filter(|&y| y)
+        .count()
+        < 2
+    {
+        return false;
+    }
+
+    true
+}
+
+fn next_password(password: &str) -> String {
+    let mut next = String::new();
+    let mut increase = true;
+
+    for c in password.chars().rev() {
+        match (c, increase) {
+            ('z', true) => next.push('a'),
+            (_, false) => next.push(c),
+            (_, true) => {
+                next.push((c as u8 + 1) as char);
+                increase = false
+            }
+        }
+    }
+    if increase {
+        next.push('a');
+    }
+    next = next.chars().rev().collect();
+
+    if next
+        .chars()
+        .filter(|x| vec!['i', 'o', 'l'].contains(x))
+        .count()
+        == 0
+    {
+        return next;
+    }
+
+    let mut nnext = String::new();
+    let mut found = false;
+    for c in next.chars() {
+        match (c, found) {
+            (_, true) => nnext.push('a'),
+            ('i' | 'o' | 'l', false) => {
+                found = true;
+                nnext.push((c as u8 + 1) as char);
+            }
+            (_, false) => nnext.push(c),
+        }
+    }
+    nnext
+}
+
+pub fn part_one(input: &str) -> Option<String> {
+    let mut password = input.to_string();
+    while !allowed_password(&password) {
+        password = next_password(&password);
+    }
+    Some(password)
+}
+pub fn part_two(input: &str) -> Option<String> {
+    let mut password = input.to_string();
+    while !allowed_password(&password) {
+        password = next_password(&password);
+    }
+    password = next_password(&password);
+    while !allowed_password(&password) {
+        password = next_password(&password);
+    }
+    Some(password)
+}
+fn main() {
+    let input = &aoc::read_file("inputs", 11);
+    aoc::solve!(1, part_one, input);
+    aoc::solve!(2, part_two, input);
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        let input = aoc::read_file("test_inputs", 11);
+        assert_eq!(part_one(&input.trim()), Some("ghjaabcc".to_string()));
+    }
+    #[test]
+    fn test_part_two() {
+        let input = aoc::read_file("test_inputs", 11);
+        assert_eq!(part_two(&input.trim()), Some("ghjbbcdd".to_string()));
+    }
+}
diff --git a/src/helpers.rs b/src/helpers.rs
index 2c1df5c..035ace6 100644
--- a/src/helpers.rs
+++ b/src/helpers.rs
@@ -25,3 +25,6 @@ where
         })
         .collect()
 }
+
+pub const ASCII_LOWERCASE: &str = "abcdefghijklmnoqprstuvwxyz";
+pub const ASCII_UPPERCASE: &str = "ABCDEFGHIJKLMNOQPRSTUVWXYZ";
diff --git a/src/test_inputs/11.txt b/src/test_inputs/11.txt
new file mode 100644
index 000000000..0859714
--- /dev/null
+++ b/src/test_inputs/11.txt
@@ -0,0 +1 @@
+ghijklmn