diff --git a/input/day10.txt b/input/day10.txt
new file mode 100644
index 0000000..cc7943a
--- /dev/null
+++ b/input/day10.txt
@@ -0,0 +1,106 @@
+[({<(({{(([([[{}{}](<>())][<(){}>[[][]]]){{(<>{})<{}()>}}](<<<()<>><()<>>>([<>[]])><{<[][]
+<<([{([<([{<<{[]<>}([]{})>><{(<>{})([][])}[[{}]((){})]>}([[([]<>)[<><>)]{<{}[]>{[]()}}]<<[{}{}]<<>{}>>{[{}<>]
+{<<[(<{<({[{[{[][]}{[]{}}](<[]<>>[<><>])}]}[<{(<<>{}>(()()))<(<>{})(<>())>}>{{{{()()}{<>}}}}])><<{{<{[
+{({([<<<[<<<<[{}{}][<>]>[(<><>)]>[<{{}()}<[]<>>>]>>([{[[()<>]{[]<>}](([]{})[<>()])}(((())[{}])[{<>()}
+[{[<[{[(([{({[()<>](<>())}[{<><>}[[]()]])((<{}[]><()[]>>[[<>{}]{<><>}])}<[<{{}[]}{()()}>{(
+{<<{{[{{({{((([]()){{}()})){(<{}[]><()>)(<<>[]><[]<>>)}}[[[<()<>>][<()<>>(()())]]<[[[]<>]{
+[{({[{[{[[<[<[<>{}]<[]>>{<<>[]><{}[]>}]>[[[[[]<>><<>{}>](<{}[]>[{}<>])]{<{<>{}}(<><>)><<{}[]>(<><>)>}]]<{{{{[
+<<<{((({<<<[[[()<>]<[]()>](<{}()>)](({[]{}}<<>()>){{[]{}}})>{[[[{}[]]<{}{}>]{[[][]]{<>()}}]}><
+({[<<{<({{[[(({}[])[<>()])<<{}[]>[[]<>]>]([{{}[]}<{}[]>]<{()[]}<{}()>>)]<[{<[]()>[{}{}]}{[()[]]}]<
+([([[{[((<[[<[<><>][(){}]>[(()[])]]]<{<{[][]}([]())>([{}][<>{}])}<(<[][]>[(){}])(([][])<<>()>)>>><[
+{<[<<([(([<([[{}[]](()())]<{<>()}>)[<(<>{})<<>{}>>{{[][])[()<>]}]>[[({<>{}}([]{})){[()()]}][{[<>]}(
+([<[<[([([[[<<<>{}>><{()()}[{}[]]>]({<<>[]>{<>()}})](((<<>{}>{{}()}))<[([]<>){{}{}}]>)][{(
+[[({(<[{<(([<{(){}}>)({<()[]><<>()>}<<()[]><<>>>))[{({(){}})(<{}<>>{[]<>})}[[([]())[()[]]]]])([<
+[<<<{[({[<[<{[{}[]][[]<>]}>{<{{}<>}>({()[]}[{}[]])>]([<[{}()]<{}[]>>{[{}()]}]{[[(){}]{<>}]<<<
+{[<[({((([(<{({}())}([{}[]]{<>[]})><[[[]{}](()())]{{<><>}{[]{}]}>)[[({<>()}<()()>)([()<>][()<>]
+<<({({[[(<(<{[<>[]]({}{})}>)[<[{(){}}[{}[]]]<{<><>}>>]>{<(([()]<(){}>)([{}<>])){(<<>()>{[]()})(<{}{}>{{}{}
+<{({(<<{[[{<{[<>()]{<>[]}}>}([{{<>[]}{[]()}}{{{}{}}{<>[]}}])]<<(((<>[]))<<[]()>[()()]>)<<<{}{}>>{<()<
+{([{{[{<<<{<[{()()}{<>}][{[][]}{[][]}]>}<<[((){}){{}()}]{{(){}}{[]<>}}>[{<{}[]>}<{[][]}{{}[]
+{{[((<[[[<{([<()[]>[()[]]]{[<><>][<><>]})([{()}][{<>[]}{{}[]}])}[[[<{}{}>({}{})]{<()<>>({}[])}]<
+{(({[((<{(<{<<<>[]>{{}<>}>}(([(){}]<[]<>>))>[[(<<>>{<><>})(({}<>)(()<>))]])}>([<[(<[{}<>][[]<>]>[(
+<{{[(<<{{(<({<<><>>({}())}[<[]()><<>[]>]){{(()()){<><>}}[({}{}){[]<>}]}>{(<<{}()><()()>>{{<>{}}{{}<>
+{{<{({{{([{<({{}<>}{[][]}){{()[]}}><{{[]}{<>{}}}[{()<>}[<>[]]]>}[{([()]){({}<>)[<>{}])}(<<[][]>[()[]]>([
+[{<(<({<<[[(<[[]{}]({}{})><<()<>>{[]()}>)({<[]()>([]())}{{[]{}}{<>[]}})]]{[(<{{}[]}{[][]}><[(){}]<<><>>>)]}>>
+{<<(<({<{[<[{<()<>>}]<{[<><>]{[]{}}}<{<><>}>>>([[<[]()><{}()>]{{<>[]}>](<[<>{}]<[]{}>>[[()[]]{[]{}}])
+<({<{<[{([<(({{}()}(<>()))([<><>]{[][]}))><<[<[][]>{()()}]>>]){[[({{[]}}{[()()]}){[(()[])[{}()]](([]<>){<><
+[({{([<[({<((({}[])(<>()))<[<><>][{}{}]>)[[([]{})<<><>>]((<>{})([]{}))]>(([[[]()}{<><>}][{()[]}]){{<{}{
+<{({[[{({((({([]<>){<>[]}}{{<><>}})(({()<>>[[]{}])<(()[])[[]{}]>)))})[{<<({[<>()]})([[()[]]<{}
+{({(<(<([{{{(<{}>)<{[]()}[[]()]>}[([<>{}]{[]()})[[{}](<>[])]]}{[({{}{}}[{}()])([{}()]{<>[]})]{[(()[])(()
+{<{{<[[({[{<({()<>}{()<>})>{[{()[])[()[]]]}}][({<<[]<>>[()[]]><<{}<>>[{}()]>})]})<[({<({[]()
+<<(<{[<[(({{<(()[])<{}{}>><(<>{})<{}[]>>}[<([]())({}{})><<()[]><()[]>>]}<[[{(){}}{<>()}]{((){}){<><>})]<
+<<<((([{({<{<[(){}]{(){}}>}{<(()<>)<{}{}>>}>[([<<>()><<><>>])<(([]{})){<{}[]>[{}()]}>]}[{{<<()[]>(
+({{([[<[[<<{({()()}({}[]))}[{(()[]){{}<>}}{([]<>)(()())}]><<{{{}[]}}{[[]](()()>}>{<({}[]){[]
+<[<[[<[[<{{{<{<>()}[()[]]](<{}[]><<>[]>)}<<<{}()>([]<>)>{([]{}){[]<>}}>}([{{<><>}[[][]]}{[<>
+{[[{[<{{[{{[[<{}[]><<>>]]}<<<{()()}([]<>)>{<<>[]>[<>[]]}>([{()[]}{[][]}]{{{}{}}(<>{}}})>}<((<<()[]>>[<()()><[
+([(<{(({[([([[{}]])]({<(()())<<>{}>>}<<{{}()}>[<<>()><<><>>]>))<{{{{()()}[(){}]}>}>]})<[<<{<[<{}{}><{}{}>]{{
+{{{<[{{([<[<([{}[]]({}<>))[([]())]>](<(<()()>[<>])>{[(()<>)]({<>[]}(<>{}))})>{({[{[]<>]<{}{}>]<[{}<>]<<
+<{<<<([([{<[(([]{})(<>)){(<>{})<<><>>}]{({<>[]}{{}()}){{{}{}}{{}()}}}><[<(()){[][]}>{<{}{}>{<>()}}]>}][[
+([({{({{([[{[{[]()}{[]{}}]<<[]<>>(()<>)>}[((<>{})[<>()])[[{}()]<<><>>]]]][<[<(()<>)(<>)><[<
+[<<{[(<[<<{{{<<>{}><<>[]>}}}>((<[[()<>]<<>()}]<(<>()){<>()}>>([(()<>)([]{})][[(){}]{{}{}}]))[{[[[]{}]]<
+<{<{<<[([[(<[[[]()]<{}{}>][{[]<>}(()[])]]({{<><>}(()[])}{([][])(()())}))(<[[<>{}]][{()<>}]>)][<{<(
+[{[[[[((<[[((<[][]>{(){}})[{()()}])]{<<{(){}}>{(<><>)(()[])}){<[()]<[]()>>}}]>))[[<{([{{()<>}{()
+([{({<<{[(([(<[]<>>{[]()})](<{{}{}}[()()]>)))[[<{({}())}{<()[]>}>](<([[]{}][<>{}])<{{}{}}[()[]]>>[<
+([[<{[[{[[<{{[{}[]](<>{})}([()<>](()[]))}>(([{[][]}<<>()>]((<>{}){<>[]})))]([([{{}[]}([]()))(<{}()><<><>>))[
+(<<[{<<<{(<<([()][(){}])({[]{}})>{<{{}<>}{()()}><[{}[]](<>[])>}>{[[{()()}[[]<>]]<<{}()><[]{}>>](<{<>[]}>{<<><
+{<(<({{[({[{{{(){}}[<>[]]){[<><>]{[]()}}}<<[[]<>]{{}<>}>{((){})([][])}>]}<{<((()){[]()})<{<>(
+[[[((({{[[{(<[[][]]((){})>){[([]{})]<<{}<>><()[]>>}}<((<()()>))[{([]())([][])}[<()>{(){}}]]>][{(<<<>()><(){
+{<<<{{(({{{<({{}[]}({}<>))<{{}}>><({<>{}}{<>{}})>}[([[<><>]<[]>](({}{})<(){}>))([<{}[]>[()[]]]
+[((([(([{{{([{<><>}]<((){}){{}[]}>)<([()[]]{[][]})<{{}()}{[][]}>>}}}(<<<<<()<>>[{}[]]>>>{<[
+[{(<[[{{({(({((){})((){})}{(<>{})<[]{}>})([(()[])<()[]>]))[([{()[]}[[]<>)])<{{()<>}(()())}<{[][]}[{}<>
+<(<(<([(((<{(<<>{}>[<>{}]){<{}<>>({}<>)}}(<<<>[]>[()()]><{[][]}>)>)))[<{(<{([]{})[[]{}]}[<{}{}><()()>]
+<<(<([<[(<<{[[()[]]([]{})]}[[((){})<{}()>]<<[]<>>({}<>)>]><(<{<>()}<[]{}>>(<{}{}>(()<>)))>>){{([<([]{})<{}{}>
+<{<{{{(({{<[[([]<>){{}<>}]{{[][]}}]>{<<{()<>}({}[])>{{{}()}{(){}}}>}}[<(<([]())<<>()>>[{[]}{<>[]}]){[[{}<
+[{(<(({(<<{[[({}()){<>{})]]}[[{[<>[]][{}[]]}]((([][])<(){}>)[{[]{}}(<>())])]>>[(((({(){}}<{}>)(<{}{}><[]
+{(([[[(<<<<<{<<><>><{}[]>}[[[]{}]([]<>)]>{{{<><>}<[]{}>}[<{}<>><()<>>]}>>[{{<{<>}(()<>)>[{{}<>
+{([{[([<[<<[[(()()){()()}](([]()){<>()})]>({<<{}()><<>()>><[<>{}]{{}<>}>})>]{{(<(<[]<>>{<>
+{(({{<[[{([[{[[]()][{}{}]}{[()<>]<()[]>}](<({}[])>{[[]{}]<<>[]>})]{{({{}<>}<(){}>){<{}()>({}{})}}[[{
+{(((<<{<([[{([()[]][[]<>])}{{[<>{}]<{}()>}<<<>[]>[<>{}]]}](({[()()](<>{})}[<()>]))]{{[[[[]<>]{<>
+([[[({{(([{{([<>{}]){<{}{}><{}[]>}}<[[(){}][[]{}]][(())[<>{}]]>}])[{([{{<>()}[[]<>]}{[[]()]{[][]}}]{{{
+{[<(<<{<{<[([(()())[<>()]]{{{}<>}{[]<>}})]>}>}{{<([<<<[]()><{}()>>([[]()]([]()))><{<<><>>([]<>)}<(<>
+<[<(((<[(<[[[<<>[]>{()[]}][{[][]>(<>)]](<{<><>}[()]>)]>{<{({{}{}}[{}{}]){[[]<>]<{}>}}[{({})
+[{<[[[<[[[<[{[<>[]]{[]()}})<<[[]()]{[][]}>([[][]]{()()})>>]]([[({[<><>][<>]}{<<>()>([])})<([{}<>][<>()])<(
+{((<[<(<(({([(()<>){[]}]<[{}<>]{()<>}>)([([]{})][{(){}}[[]<>]]]}<<{{()<>}(()[])}<(<><>)<()>>>>)({{[<(){}>[
+[([{<((([[<<[{{}{}}({}<>)]>><<[[[]()](<>())]>>]([([({}<>)](<{}<>>))<[[{}{}]]>]<[<[[][]]{()()}><{{}<>}((){})
+([[[{{[[({{{{{()<>}{[]{}}}}[<<()[]><[]{}>>[[<>()]]]}{<[{(){}}(<>())][<{}<>><[][]>]>{<([]{})[()()
+[<(<<({(<[[{[{()()}{{}{}}][[<>()>]}{[[<>{}](<>[])]}]([{([][])<()>}{<<>()>[()<>]}]{{[[]][[]<>
+[<<({([<{[{(([{}()]<<><>>))}[({<[]()>([]{})}[{()()}(()<>)])(<([][])(())>{<[]()>{[]{}}})]]{[<({<><>}<[]
+<{({(<{{(<{([[<>{}]])<<[()[]]{<>{}}>>}{[((()<>))<(()())>][{{[]{}}[<>()]}(<<>{}>[()()])]}]{{({<{}
+(<{{[<[[{[<{{[{}()]}{({}{})}}(<{[]()}({})><<[]{}>(<>[])>)>](<{[(())({}{})]((<>[]){()<>})}[{[[]<>][{}[]]}[
+(<<{<[[{(([{[(<>{})([])]<[<>()][<>[]]>}]<[([[]()](()[]))({(){}}<(){}>)]<{{{}{}}<[]<>>}<([])([]<>)>>]))}]{
+[([{({{((<[[([{}[]]{<>}){(()[])([]{})}][{<{}<>><()()>}]]<([(<>{})[<>[]]])]>))}[((({(([[][]
+<[{<<[{{<{{[{[()()]{()[]}}][([{}<>]<()<>>)<[{}{}]>]}{<[(()<>)][((){})({}())]>((<<>{}><<>()>)<[{
+([[{[<[{[<[([({}[]){{}()}]){({[][]}(()))[<[][]>{{}<>}]}]>]}(({{({<{}<>>[[]<>]}{{()}})({[<>()]}<{{}}>)}[
+([[[<[<(<<<[{{[]}<<>{}>}[(<><>){{}[]}]><[{{}<>}<()()>][[{}()](<>{})]>><[{{()[]}<{}>}<[<><>]({
+([(([[[<{<<<{([]){[][]}}{(<>[])[{}()]}>[<(()[])[()[]]>(<()<>>(()<>))]>([<{<>{}}<{}[]>>(<()[]><{}
+(<[{<<(<<({<[(())([]<>)][<()[]><{}<>>]>({<{}{}>{{}}}{(<>[])<[]{}>})}){[({[()()][[]{}]}[<<>[]>{{}
+({[{(<(([(<[{<[]<>>(()())}[(())[{}<>]]]<{{()[]}{()()}}>>[<<[{}{}][{}{}]>((()()>[{}()])>[[<<>{}>(<
+(([(<<([<[({(<{}()>)({<>{}}({}<>))}[({{}<>]{[]()})<{[]<>}>])<<[{{}()}{()<>}]{<()()>{<>()}}
+[((<{<([{{<<<(()[])(<>())>{<{}()>(<>())}>[<<[]>({}())>]>({<[{}<>]{<><>}>})}}])<<[<{([{[][]>{()()}
+<[({(<[{{[[(((()<>)<{}[]>){<[]()>[[]()]})<[[{}()](()<>)]<((){})>>]]<(({(<>[])([]{})}[{()}[()()]
+(<[{[<(<[([[(<(){}>{{}())){(<>{})[{}()]}]<<({}[]){[]()}>(({}{}){{}{}})>](<{<[][]>([]())}[<()>{<>
+{<[[<((((({({[{}[]]{<><>}}({<>()}{{}<>}))([[()()]([]{})]{[{}]{<>()}})}{<((<><>)(<>[]))[[{}()][{}[]]]><<[<>{}]
+[[[{{{(<<([(<(()[])<[]{}>>[[<>{}]<{}>]){<{[]()}(()<>)>([{}[]][{}<>])}])(<{<<{}[]>{<>{}}>([()[]]<{}{}>)
+{<[(({[[((([{(<>[])<<>[]>}[<()[]><{}{}>]](<([]{})(<><>)>{{()}({}[])}))))([[(([<>{}][{}()]))<{{{}()}<{}[]>}
+<<<<<<<[{<[({{{}[]}<<>>}[<{}<>>([])>)<{({}[])}<({}())>>]{{{{{}()}}}}>{<[(({}[])(<><>))](<{()<>}>([{}{}][[]{}
+[[(<(<{<([(<[[[]{}]{[]{}}]<[{}<>]<{}<>>>><{<()[]>({}())}([()[]]{()})>){{{{<>{}}<()<>>}(<{}()>([]
+(<<([<(([([{[[<>[]](<><>)][[<><>]{{}[]}]}[{<()()>}]]){([((()()){<>{}})(({}()}([]<>))]{<{<>()}(
+({({<(([(([(({{}<>}{(){}}){{()[]}[{}<>]})[[{()()}{()()}]((()))>]{({([]{}){{}[]}}{<{}()>[{}()]})(<[[]{}]{
+[{[{<[[((<[(((<>[])([]<>>)({()<>}))][{<({}[]){<>{}}>}(<{<><>}{{}{}}>{<()[]>{(){}}})]>))[{{{
+[<(({[<<<{(<[<(){}>{[][]}][[()<>]<{}{}>]>{{<[]{}>[()[]]}{({}[]){[]<>}}})((({<><>}(()))[([]{})]))}{<<({{}{
+({([<{{((<({([{}<>]([]{}))(<[]<>>{[]()})}<[([]{})[[]{}]][(()<>)<[]<>>]>)[(<{[]<>}<{}()}>[({}<>)<<>{
+[<[(<{([(([(<[{}{}]{{}[]}>[([]())[()()]])(<{(){}}{{}{}}>)])([{<<[]{}>>{{[]()}[{}{}])}][{{{{}<>}}}
+{(<{((<[[[({[((){})]}{<({}<>)(<>())>[<{}<>>([]<>)]})][{<{<[]{}>{()[]]}(([]{})<<>()>)>([{{}<>}<[][]>]{
+<{(([<([({[(<(<>{})[[]<>]><[[][]]<{}[]>>)](<{{{}<>}(<>())}<[<><>]([]())>>([[()[]]<<>{}>]))}<
+{{([<<({[[<<<{()[]}<{}()>>[[(){}>{<><>}]>[[{[]}]{({}<>){{}{}}}]>[[{<[]<>><()<>>}<{<>()}>]<{
+([{<{<((([<[(<[]{}><<>()>)(({}<>)[[]<>])]><{[(()())[()()]]}>]<({{<<>[]>[<>{}]}[[()<>]]])[[<({}[])({}<>)><
+[<[([(<([[<[[[()[]][[]<>]][<{}<>>]](([{}{}])[{[]{}}({})])>[<<({}()){<>[])>{<<><>>(<><>)}>]]{{{{({}<>)<<>
+<<({[<{[({{[[<[]()><<>>][<()[]>[{}<>]]]}<{<[(){}]{[]{}}>({{}<>}[<>[]])}{<{[]()}<<>()>>{(<>[])[{}
+{{<{({{([{<<<{<>[]}(<><>)>[<<>[]>({}{})]><<{()}[{}[]]>[<()[]>{<>{}}]>>{{[<{}()>(<>[])]}[(<[]()>(()))
+[({(([(([{<<{[<>{}]({}{})}{[[]()]{[]{}}}>>}}<{<{<((){})(<>[])>{([]())<{}<>>}}<[<()>][<(){}>{
+(<<[<<({([([(<[]<>>{{}()})([()<>][()<>])](<({}{}){<>{}}>{(<>{}]{{}()}}))]{{[[([]())<[]<>>]
+<[[{{({{{<<[<<[][]>{<>()}>{{()()}([]<>)}]<[{()[]}{()}][[[]]]}>>}<<[{{{<>[]}<<>{}>}({{}()}{[][]}
+[{<{[[<[<([((<{}<>><<><>>){<[]{}>[{}{}]})[[([])[[]()]]({<><>}<(){}>)]]{<((()[])([][])){(<>())([][])}>[{
+<(([{<[<<[{<[[[][]]](<[]<>><<>[]>)>([{(){}}{{}[]}]{<<>[]><{}()>})}<{{([][])[{}<>]}{{{}()}}}[<(<
+<<{((([<[(<[{<[]()>}{(())<()<>>}]>[{<[<>()]{()<>}>[{<><>}{[][]}]}{[<{}{}>({}<>)]{{[]()>{[]<>
+[[[{[[[{{<(<{{[]<>}[<><>]}({()()}[()[]])>[((<>[])(<>)){{()<>}([][])}])[{{{[]<>}<()[])}({<>[]})}(({
+{<<<(<(((({[[([])([][])]<<[]<>>>]}{{<{{}[]}(<>[])><{[][]}[[]{}]>}<{<()[]>}<{[]{}}{()<>}>>})){<<<[{[]<>}[[]
diff --git a/src/day10.rs b/src/day10.rs
new file mode 100644
index 0000000..9c95e81
--- /dev/null
+++ b/src/day10.rs
@@ -0,0 +1,156 @@
+use std::collections::VecDeque;
+
+pub fn day10() {
+    let corrupted = "{([(<{}[<>[]}>{[]{[(<()>";
+    let result = parse_line(corrupted);
+    println!(
+        "corrupted: {:?}, score: {:?}",
+        &result,
+        error_score(&result)
+    );
+
+    let incomplete = "[(()[<>])]({[<{<<[]>>(";
+    println!("incomplete: {:#?}", parse_line(incomplete));
+
+    // let input = r#"
+    // [({(<(())[]>[[{[]{<()<>>
+    // [(()[<>])]({[<{<<[]>>(
+    // {([(<{}[<>[]}>{[]{[(<()>
+    // (((({<>}<{<{<>}{[]{[]{}
+    // [[<[([]))<([[{}[[()]]]
+    // [{[{({}]{}}([{[{{{}}([]
+    // {<[[]]>}<{[{[{[]{()[[[]
+    // [<(<(<(<{}))><([]([]()
+    // <{([([[(<>()){}]>(<<{{
+    // <{([{{}}[<[[[<>{}]]]>[]]
+    //     "#;
+    let input = include_str!("../input/day10.txt");
+
+    let parsed_lines = input.trim().lines().map(parse_line);
+
+    let total_error_score: u64 = parsed_lines
+        .clone()
+        .filter_map(|res| error_score(&res))
+        .sum();
+    println!("total error score: {}", total_error_score);
+
+    let completion = autocomplete(&parse_line(incomplete)).unwrap();
+    println!(
+        "to complete: {:?}, score: {}",
+        &completion,
+        autocomplete_score(&completion)
+    );
+
+    let mut autocomplete_scores = parsed_lines
+        .filter_map(|res| autocomplete(&res))
+        .map(|completion| autocomplete_score(&completion))
+        .collect::<Vec<_>>();
+    autocomplete_scores.sort();
+    println!(
+        "middle score: {}",
+        autocomplete_scores[autocomplete_scores.len() / 2]
+    );
+}
+
+static OPENERS: &[char] = &['(', '[', '{', '<'];
+static CLOSERS: &[char] = &[')', ']', '}', '>'];
+
+fn parse_line(line: &str) -> ParseResult {
+    let mut iter = line.trim().chars().peekable();
+    let mut finished = vec![];
+    let mut in_progress: VecDeque<Chunk> = VecDeque::new();
+    while let Some(c) = iter.next() {
+        if OPENERS.contains(&c) {
+            let index = OPENERS.iter().position(|&e| e == c).unwrap();
+            let new = Chunk {
+                opener: c,
+                closer: CLOSERS[index],
+                chunks: vec![],
+            };
+            in_progress.push_front(new);
+        } else if CLOSERS.contains(&c) {
+            if in_progress.front().unwrap().closer == c {
+                let closed = in_progress.pop_front().unwrap();
+                match in_progress.front_mut() {
+                    Some(new_cur) => new_cur.chunks.push(closed),
+                    None => {
+                        finished.push(closed);
+                    }
+                }
+            } else {
+                return ParseResult::Error {
+                    expected: in_progress.front().unwrap().closer,
+                    found: c,
+                };
+            }
+        } else {
+            panic!("unreachable");
+        }
+    }
+    if in_progress.is_empty() {
+        ParseResult::Chunks(finished)
+    } else {
+        ParseResult::Incomplete {
+            finished,
+            in_progress,
+        }
+    }
+}
+
+fn error_score(result: &ParseResult) -> Option<u64> {
+    match result {
+        ParseResult::Error { expected: _, found } => Some(match found {
+            ')' => 3,
+            ']' => 57,
+            '}' => 1197,
+            '>' => 25137,
+            _ => 0,
+        }),
+        _ => None,
+    }
+}
+
+fn autocomplete(result: &ParseResult) -> Option<Vec<char>> {
+    match result {
+        ParseResult::Incomplete {
+            finished: _,
+            in_progress,
+        } => Some(in_progress.iter().map(|chunk| chunk.closer).collect()),
+        _ => None,
+    }
+}
+
+fn autocomplete_score(completion: &[char]) -> u64 {
+    let mut score = 0;
+    for c in completion {
+        score *= 5;
+        score += match c {
+            ')' => 1,
+            ']' => 2,
+            '}' => 3,
+            '>' => 4,
+            _ => 0,
+        };
+    }
+    score
+}
+
+#[derive(Debug)]
+struct Chunk {
+    opener: char,
+    closer: char,
+    chunks: Vec<Chunk>,
+}
+
+#[derive(Debug)]
+enum ParseResult {
+    Chunks(Vec<Chunk>),
+    Error {
+        expected: char,
+        found: char,
+    },
+    Incomplete {
+        finished: Vec<Chunk>,
+        in_progress: VecDeque<Chunk>,
+    },
+}
diff --git a/src/main.rs b/src/main.rs
index fcf2c16..c90783c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,7 +8,8 @@ mod day06;
 mod day07;
 mod day08;
 mod day09;
+mod day10;
 
 fn main() {
-    day09::day9();
+    day10::day10();
 }