@@ 27,7 27,7 @@ fn count(s: &[u8]) -> (bool, bool) {
         assert!(c >= b'a' && c <= b'z');
         freqs[(c - b'a') as usize] += 1;
     }
-    freqs.into_iter().fold((false, false), |(two, three), &c| {
+    freqs.iter().fold((false, false), |(two, three), &c| {
         if c == 2 {
             (true, three)
         } else if c == 3 {

@@ 36,21 36,14 @@ impl FromStr for Claim {
 fn main() {
     let v: Vec<Claim> = aoc::file::to_single_parsed(INPUT);
     let mut m = vec![[0; ARSIZ]; ARSIZ];
-    for &Claim {
-        no: _,
-        x,
-        y,
-        xl,
-        yl,
-    } in &v
-    {
+    for &Claim { x, y, xl, yl, .. } in &v {
         for i in 0..xl {
             for j in 0..yl {
                 m[x + i][y + j] += 1;
             }
         }
     }
-    let sum: usize = m.iter().map(|r| r.iter().filter(|&x| x > &1).count()).sum();
+    let sum: usize = m.iter().map(|r| r.iter().filter(|&&x| x > 1).count()).sum();
     println!("  1: {}", sum);
     println!("  2: {}", find_claim(&m, &v));
 }

@@ 41,7 41,7 @@ fn main() {
     let data: Vec<Vec<i16>> = aoc::file::to_split_parsed(INPUT);
     let mut data = data.into_iter().map(|b| b[..].into());
     let mut state: State = Default::default();
-    let mut map = FxHashMap::default();
+    let mut map = FxHashMap::<i16, Vec<(u8, u8)>>::default();
     loop {
         match data.next() {
             Some(GuardEvent {


@@ 71,13 71,11 @@ fn main() {
             None => break,
         }
         if state.f.is_some() && state.w.is_some() {
-            let e = map.entry(state.g).or_insert(vec![]);
+            let e = map.entry(state.g).or_default();
             if let (Some(f), Some(w)) = (state.f, state.w) {
                 e.push((f, w));
                 state.f = None;
                 state.w = None;
-            } else {
-                panic!();
             }
         }
     }

@@ 29,12 29,10 @@ impl FromStr for Edge {
 fn main() {
     let input: Vec<Edge> = aoc::file::to_single_parsed(INPUT);
     let mut ids = FxHashSet::default();
-    let mut deps = FxHashMap::default();
+    let mut deps = FxHashMap::<_, FxHashSet<_>>::default();
 
     for Edge { needed, needs } in input {
-        deps.entry(needs)
-            .or_insert(FxHashSet::default())
-            .insert(needed);
+        deps.entry(needs).or_default().insert(needed);
         ids.insert(needs);
         ids.insert(needed);
     }


@@ 48,8 46,7 @@ fn main() {
     {
         let mut rest = rest.clone();
         while !rest.is_empty() {
-            let mut it = (0..rest.len()).rev();
-            while let Some(i) = it.next() {
+            for i in (0..rest.len()).rev() {
                 if deps.get(&rest[i]).map_or(true, |s| done.is_superset(s)) {
                     ans.push(rest[i]);
                     done.insert(rest[i]);


@@ 72,12 69,10 @@ fn main() {
             time = *wda.iter().min().filter(|&&t| t > time).unwrap_or(&time);
             let mut it = (0..rest.len()).rev();
             while let Some(i) = it.next() {
-                if {
-                    if let Some(m) = deps.get(&rest[i]) {
-                        m.iter().all(|d| ida.get(d).map_or(false, |&t| t <= time))
-                    } else {
-                        true
-                    }
+                if if let Some(m) = deps.get(&rest[i]) {
+                    m.iter().all(|d| ida.get(d).map_or(false, |&t| t <= time))
+                } else {
+                    true
                 } {
                     for b in wda.iter_mut() {
                         if *b <= time {

@@ 37,7 37,7 @@ impl Game<'_> {
             }
         }
         self.players
-            .into_iter()
+            .iter()
             .max()
             .ok_or("empty container")
             .map(|r| *r)

@@ 22,8 22,8 @@ fn main() {
     let mut by_pos = FxHashMap::default();
     for i in 1.. {
         by_pos.clear();
-        let mut xp = (1000000i32, -1000000i32);
-        let mut yp = (1000000i32, -1000000i32);
+        let mut xp = (std::i32::MAX, std::i32::MIN);
+        let mut yp = (std::i32::MAX, std::i32::MIN);
 
         for &mut (ref mut pos, ref vel) in &mut input {
             *pos += *vel;


@@ 43,7 43,7 @@ fn main() {
         for y in yp.0..=yp.1 {
             print!("\t");
             for x in xp.0..=xp.1 {
-                if let Some(_) = by_pos.remove(&Point(x, y)) {
+                if by_pos.remove(&Point(x, y)).is_some() {
                     print!("#");
                 } else {
                     print!(" ");

@@ 66,7 66,7 @@ fn generation(line: Vec<u8>, zero: isize) -> (Vec<u8>, isize) {
     let next = line.windows(5).map(rule);
     let last = last(&line);
     let last = if let Some(p) = last.iter().rposition(|&b| b == b'#') {
-        &last[0..p + 1]
+        &last[0..=p]
     } else {
         &[]
     };

@@ 86,17 86,14 @@ fn solve_opcodes(mut map: Vec<Either<OpCode, FxHashSet<OpCode>>>) -> [OpCode; 16
                 Either::Left(op) => *op,
                 _ => continue,
             };
-            for j in 0..map.len() {
+            for (j, m) in map.iter_mut().enumerate() {
                 if j == i {
                     continue;
                 }
-                match &mut map[j] {
-                    Either::Right(m) => {
-                        m.remove(&op);
-                    }
-                    _ => {}
+                if let Either::Right(ref mut m) = m {
+                    m.remove(&op);
                 }
-                let op = if let Either::Right(m) = &map[j] {
+                let op = if let Either::Right(m) = &m {
                     if m.len() == 1 {
                         *m.iter().next().unwrap()
                     } else {


@@ 105,7 102,7 @@ fn solve_opcodes(mut map: Vec<Either<OpCode, FxHashSet<OpCode>>>) -> [OpCode; 16
                 } else {
                     continue;
                 };
-                map[j] = Either::Left(op);
+                *m = Either::Left(op);
             }
         }
     }


@@ 192,7 189,7 @@ impl Device {
             if n == 0 {
                 break;
             }
-            if l.trim().len() == 0 {
+            if l.trim().is_empty() {
                 continue;
             }
             let mut ds = DFILT.find_iter(&l).filter_map(|m| m.as_str().parse().ok());


@@ 244,14 241,9 @@ impl Test {
         }
         if candidates.len() == 1 {
             map[self.oper[0]] = Either::Left(candidates[0]);
-        } else {
-            match &mut map[self.oper[0]] {
-                Either::Right(m) => {
-                    for &op in &candidates {
-                        m.insert(op);
-                    }
-                }
-                _ => {}
+        } else if let Either::Right(ref mut m) = map[self.oper[0]] {
+            for &op in &candidates {
+                m.insert(op);
             }
         }
 

@@ 19,11 19,7 @@ impl std::str::FromStr for ClayRange {
             static ref PARSE: Regex = Regex::new(r"^(x|y)=(\d+), (x|y)=(\d+)\.\.(\d+)$").unwrap();
         }
         let caps = PARSE.captures(s).expect("string did not match");
-        let is_vert = if caps.get(1).unwrap().as_str() == "x" {
-            true
-        } else {
-            false
-        };
+        let is_vert = caps.get(1).unwrap().as_str() == "x";
         let pos = caps.get(2).unwrap().as_str().parse().unwrap();
         let range = RangeInclusive::new(
             caps.get(4).unwrap().as_str().parse().unwrap(),

@@ 52,8 52,8 @@ where
         .map(|v| {
             let v = v.expect("error in read");
             match v.parse() {
-                Err(_) => panic!("parse error for input: {}", v),
                 Ok(vp) => vp,
+                _ => panic!("parse error for input: {}", v),
             }
         })
         .collect()


@@ 70,8 70,8 @@ where
         .map(|s| {
             s.split_whitespace()
                 .map(|v| match v.parse() {
-                    Err(_) => panic!("parse error for input: {}", v),
                     Ok(vp) => vp,
+                    _ => panic!("parse error for input: {}", v),
                 })
                 .collect()
         })


@@ 89,8 89,8 @@ where
             s.split(f)
                 .filter(|s| !s.is_empty())
                 .map(|v| match v.parse() {
-                    Err(_) => panic!("parse error for input: {}", v),
                     Ok(vp) => vp,
+                    _ => panic!("parse error for input: {}", v),
                 })
                 .collect()
         })

@@ 113,7 113,7 @@ impl<T> Iterator for BfsIntoIter<T> {
         if let Some(Node { data, sub_forest }) = match self.cur.next() {
             None => {
                 if let Some(v) = self.rest.pop_front() {
-                    assert!(v.len() > 0, "length should always be greater than 0");
+                    assert!(!v.is_empty(), "length should always be greater than 0");
                     self.cur = v.into_iter();
                     self.cur.next()
                 } else {


@@ 123,7 123,7 @@ impl<T> Iterator for BfsIntoIter<T> {
             something => something,
         } {
             self.next = Some(data);
-            if sub_forest.len() > 0 {
+            if !sub_forest.is_empty() {
                 self.rest.push_back(sub_forest);
             }
         }

@@ 28,4 28,8 @@ impl UnionFind {
     pub fn len(&self) -> usize {
         self.0.len()
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
 }