diff --git a/data/day06/example01.txt b/data/day06/example01.txt
new file mode 100644
index 0000000..848af1c
--- /dev/null
+++ b/data/day06/example01.txt
@@ -0,0 +1 @@
+nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg
\ No newline at end of file
diff --git a/data/day06/input.txt b/data/day06/input.txt
new file mode 100644
index 0000000..99f31cb
--- /dev/null
+++ b/data/day06/input.txt
@@ -0,0 +1 @@
+jfnjjwbbqttplpvllqgllmdllfmllscssqmqzmmwzznqnwqnwnqnjjbdbpbtbdbzzzljljzjjpccrmmppzfpzfpfnfccfbbcqcrcffblfbftbfbtbwwwmgwmgmnngnllnfllhghcghhjppchcfcnfffllmmqbmmpwwwwlqwwqgqcqsqjqpqzqqdzdtztltslsljjfqfcqqgbqqqghqgqvgvrggqwggrgjgmmnrmmzgmzgzpzjjctcmtcmcnndppcvpvrrwvrvhrvhrhjhnjnvjnjrjggccvffnqqvfqvvnmvmqmfmfqqzfzbfzzzgpzpllrwwnpwpnwnwgwhhrrdnrrdjjzjszsjjbddcdbbvmbmqbqnbqbsqbsqqwbwhwggssdnnmttvnnvmnmhmfhhjchcttzdzdqqszzcwwhhwzhwhphqhcqqsggddfmmvzmzwmwfwzwrrbmrrnwnfnwnlwnwrwfwnnmtnnzwnwdnnbhhrphrhlhwllpmmbcbtbffmqffddjnjwwzpzfpptbbqqwbwzbzjbjmjljblbtlblqqhqbqggrngrgllbmbccmhmqmqwwqcqssqzzfjzjrjnnqrqssfnsnvvtgvvmsvsqqljjbsbrrjllvfvzfzmzhzzhthjhshlslfljfjqjpqpvvmpmhpmhmqqmmdwmddppjlplhlsstlssgnggrbblggffcdfdzzwqqtztqtwqtwtzzsjsbszsbsvbvwwjqjnnpdpccwssvdsdzzqbqbtbtqtmtltltvlvddzwzzfpzpjpgphprpgpqqwppdwpdplddvffcdffvpvqqgvqgvvrfvrvqrrcjcpjjpttftqqvjqvqsvqsvqssdpdbbbmcmscsddbhhgttwhhjlltqllnqntqtsscnntwwhswswlwggldltlttsjszsnznsznzccbtbblplnnmfmqmrrvjvhjhzhnzzgnnhrrdrllblpbllfdfjjssvnssvlsllnqqhwqhhhsgstsjstthrrhrghrhhfmhmwhwrwwsrwrfwwdnntqnnsvnvmnnfvnntztqzqhqnqjnnjfflbfllrsllqhqdqccgvgnvvcwcfccmssqnqhhqrrfrtrvvnjnpjnjjpplmlppvmpphjhppvhvdvssjcjrrtrdrrsvvbbjzzrtztgzghzhccwmccshhzbhhdwdwsdswwlcwllpblpphrppfhfnffrbbcgcmggnvnzzmvvcrrftrftrffcscvcsslbljlglzgzbzczszmsmbmnbbhdhvvsqvqhvvfrfddbpwgvztwwqcpzhhwnhphnrwldjmztsptbbgsqbqqccwbdqzvhfjlfldgphzbfprclgpfztbrgvsvfpghmdchscbdqjqgzvmrtdrfzbhgdvgznjcsmglcfwhdtpsljnvvzjcbbrczwtgpdmgpzhctvbbmvsjzthffsjqhfsdrclpqslbhnmpczwvggpzbjcchfjzjhhgtrmlgnzlndfvzrccgggrpmprbmjbfjjhzrhrtwgqdbgdlqghssrnmtmpvttcqwnwdzhgfnddgbqcsdvzvwqdnmmpwrwhfbqtcpqhvwbczrmjqzsntvdrncwjsmvvwcngrtlwtjmnctwrrtvphbjhlqmgzfsfsrblzzvmzlbhzjhwbdfpncdrfchmrqhspdszcjrnvwtmjzmsmzcdphsdzjgqswwrpdvlpvrdnhplnlmswvcrzlcmbtqtscjfwrnrctrvdqcqzwcvgvpdgrndrgsrvzftwpqjjgjhzwhvrjlqntdtcjdrqzhqlqqdffcgvttlhvwgggnwmdlvghfgjpsmntbvbjbbttrwsljwsrvtmznvqdptpwtdcwtcsfdjlmdqthqggjcptrqhbsbjzqqmvvjmgmppqmjmnjdqvspzlbgzjsjshpslmszqnzghsszpsmpzfcrqqjdwvtbnzstvvjzvtzgpptcmvmbvmpvpzvgfnwtlmdzhvhshtwvnbgwmtzqhcptflpqsqvmptchpfcbwhvjzdcnsnqrgdwfcthqfssnbqnvgvvhlzqfqmdlcwnshtvhhhpghjbmhdbfbqcvbnbvwbzcbbmjnrqmsdqnmnbsrvhggzsrlbwtfmgwrnlhrbrrrqdcspnrpnppngrtdqtbmbhcbjrlhpfjpdnfndmqvwvhlgmsntpwrlrwwqhwvzbpzqqggnbqlsjjqtbqjcdpmndgmtdhfbqrpdzzsnmhzmqqnbdqftqmnhfbdzdlfwgjsjhrcsmtfzgwbvbbzdrlbmcgmppqfppmbqrnsmrmhrdsvgcfmzpfnvrbbgfccfcbphszwdbnnwcjjvvlpdtfzgtslvgqwmsvlpzjcbqwqclrjrsgthhtqrqrhvsdfjntgllsvslrvdtnsdmrgtqcmswnqwlrwlfmcfftbjpvdnmczqzldsssszhjtqtqvqtwhjcqchjvqvntvzzzprbmjcctsqfdcvpbtsgnnsqtqnmjhrgqcjnzrdsgrbtdpqjbgcmnfwhnsrfwcdmncjzwcngfbmmrsbvgvvqpvrdjfsqwjdmqjdpzcbjjfmzjjgbnwqgrvpmbzdhsgtldrzvglscfwbmjltcrzrgdslgprwscwbrhtdtglznjdcvfjzjjqzntdqdbcrcbbmvnzdshjzcsfsgpghmgdqdwsnwjtvtbqbqccbcwjpnhdhzcvdssvnvqtvzwprhpgftdwwvgsbnlzzjppcrrwmrsthvjjrvrsdrbdqfgsjsmwfplpstrbnpdhhcblhjfwzngmhlwbvnfcbgwshspsbbgbldrvmcnczszpgnddrfwrtgcqjggrrcbjwrdjlrvtspbftrtjbzjwchpfnjctcjtwtpmtblczcftqlphdjczfrvtzlsglpvhqsqqblttdjrlczhrqsgpggmvnhpqtrfbpgvzftwtsmwhwswtpvtwnsshmlcffpcjshqhqqsjtpbgszscmcbnhjjtjmpgfdhgmljqmmwlfptstjjvqhcbjpjpwzwqflhslclzzjlmcttbsncqmfzhgnzwbdtnvfwbtztwbhtfsqjfzwmfflmbwnqzqhcjwdpbvngsgzlwvwcqhqjsndznbbdcqqhmjjpqjbsnvwztgmqwdcbbjvcndmhsbvbjnzlbscmgnjcrrwrfdljtcsgmwtffgcjflpzzdcnzvmrbnrjbbmhzqqjtgsrwqmmrhpndwlbnrtrhhpqlmdrcrtdmzsslrmffpftdjvfcpvvhzhjhqtrrsclvtbsccgmmqrjbqgbmpnbzlsncssdhmjppjptvddfgbbnjzjjldjlqjzhhttsclrmsgzctwjqqvtjlfzwgtffgrdjzwdcnrprlcswffghngrqcgsbzqhhvbfjtwcjlrrmbtqjdrgpnbftnmzqnndnqwgrqndlwmjnnspbhjlnzrnptnrmcjhpbfcqpvbchvdwthjlcrfpssgtfbsgfrftcrwttrspbsvzpvcczmdqslcdgfljvtjsdpjnwmdvfzfllrdrbgvpltzlqcrlwbncswhfvrdthspmhfhfdlvpbcqlmjfznhnqblffftgzqrtswnmtnvjprqqhhhvrscvbbzgmnlnprghfdjqbgjppjzjrnclfdssbmgspwcscnlcrrqmtlljrmcwgdgcqwvvjzvsjdjvsspszlcthwzrwqtzdgmqvnlvvzrvrpqqwswzcchncrpnjdmflvmhhwvrrstpvnszfrmvpdtpqpbdmwvvbbpjnwmtststtlcvqdnvqqphzlhhzbbbjssgdcnhlmwrzwvwmcmgrcngqzcnffqzfnvldpdjmsspgpbrzhnszfnljfcrgsjvqjjbstvghlcslhqlzhltpglwffrzfgjghssfgrptbnpbhqnhhfbjsnmsvltqpthdmzzrhrhhmzlplvrtdqfrfrppdpqnllblcfjqpdwznsbrhcncdpmztcrjrfnlwtznrmpbzqsbrqrbnthgfpshrdhnwjmrnsmsfqwdjsmsvhfrbdpjrwcvmdvvmdtfqjgmdsrqtctsdmznngbsrfjvhllgwt
\ No newline at end of file
diff --git a/src/days/day06/mod.rs b/src/days/day06/mod.rs
new file mode 100644
index 0000000..7a04a3f
--- /dev/null
+++ b/src/days/day06/mod.rs
@@ -0,0 +1,119 @@
+use super::template::{DayTrait, ResultType};
+use thiserror::Error;
+
+const DAY_NUMBER: usize = 6;
+
+pub struct Day;
+
+impl DayTrait for Day {
+    fn get_day_number(&self) -> usize {
+        DAY_NUMBER
+    }
+
+    fn part1(&self, lines: &[String]) -> anyhow::Result<ResultType> {
+        let count = find_marker(&lines[0], 4)?;
+        Ok(ResultType::Integer(count as i64))
+    }
+
+    fn part2(&self, lines: &[String]) -> anyhow::Result<ResultType> {
+        let count = find_marker(&lines[0], 14)?;
+        Ok(ResultType::Integer(count as i64))
+    }
+}
+
+#[derive(Debug, Error)]
+enum MarkerError {
+    #[error("Length of Marker must not be zero")]
+    NoZeroLength,
+
+    #[error("Did not find a marker in {0}")]
+    NoMarkerFound(String),
+
+    #[error("Strings needs to be longer than marker length len({0}) < {1}")]
+    StringTooShort(String, usize),
+}
+
+fn char_pos(c: char) -> usize {
+    c as usize - 'a' as usize
+}
+
+fn find_marker(word: &str, marker_length: usize) -> Result<usize, MarkerError> {
+    if marker_length == 0 {
+        return Err(MarkerError::NoZeroLength);
+    }
+    if word.len() < marker_length {
+        return Err(MarkerError::StringTooShort(word.to_owned(), marker_length));
+    }
+    let mut letter_count = vec![0; 26];
+    let mut doubles = 0;
+    for new in word.chars().take(marker_length) {
+        let new = char_pos(new);
+        if letter_count[new] == 1 {
+            doubles += 1;
+        }
+        letter_count[new] += 1;
+    }
+    if doubles == 0 {
+        return Ok(marker_length);
+    }
+
+    for (pos, (drop, new)) in word.chars().zip(word[marker_length..].chars()).enumerate() {
+        let drop = char_pos(drop);
+        let new = char_pos(new);
+
+        if letter_count[drop] == 2 {
+            doubles -= 1;
+        }
+        letter_count[drop] -= 1;
+
+        if letter_count[new] == 1 {
+            doubles += 1;
+        }
+
+        if doubles == 0 {
+            return Ok(pos + marker_length + 1);
+        }
+        letter_count[new] += 1;
+    }
+
+    Err(MarkerError::NoMarkerFound(word.to_owned()))
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::common::file::read_lines;
+    use anyhow::Result;
+
+    #[test]
+    fn test_find_marker() -> Result<()> {
+        let input = "mjqjpqmgbljsphdztnvjfqwrcgsmlb";
+        let expected = 7;
+        let result = find_marker(input, 4)?;
+        assert_eq!(result, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_part1() -> Result<()> {
+        let day = Day {};
+        let lines = read_lines(day.get_day_number(), "example01.txt")?;
+        let expected = ResultType::Integer(10);
+        let result = day.part1(&lines)?;
+        assert_eq!(result, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_part2() -> Result<()> {
+        let day = Day {};
+        let lines = read_lines(day.get_day_number(), "example01.txt")?;
+        let expected = ResultType::Integer(29);
+        let result = day.part2(&lines)?;
+        assert_eq!(result, expected);
+
+        Ok(())
+    }
+}
diff --git a/src/days/mod.rs b/src/days/mod.rs
index 46c913b..348e9be 100644
--- a/src/days/mod.rs
+++ b/src/days/mod.rs
@@ -3,6 +3,7 @@ mod day02;
 mod day03;
 mod day04;
 mod day05;
+mod day06;
 mod template;
 
 pub use template::DayTrait;
@@ -12,7 +13,7 @@ pub mod day_provider {
     use super::*;
     use thiserror::Error;
 
-    const MAX_DAY: usize = 5;
+    const MAX_DAY: usize = 6;
 
     pub fn get_day(day_num: usize) -> Result<Box<dyn DayTrait>, ProviderError> {
         match day_num {
@@ -21,6 +22,7 @@ pub mod day_provider {
             3 => Ok(Box::new(day03::Day)),
             4 => Ok(Box::new(day04::Day)),
             5 => Ok(Box::new(day05::Day)),
+            6 => Ok(Box::new(day06::Day)),
             _ => Err(ProviderError::InvalidNumber(day_num)),
         }
     }