Optimized day 5 part 2

src/main.rs

@@ -1,14 +1,14 @@
 #![feature(test)]
 extern crate test;
 
-const INPUTS: [&str; 2] = [
-    include_str!("../inputs/sample.txt"),
-    include_str!("../inputs/input.txt"),
+const INPUTS: [&[u8]; 2] = [
+    include_bytes!("../inputs/sample.txt"),
+    include_bytes!("../inputs/input.txt"),
 ];
 
 #[derive(Debug)]
 struct Stack {
-    stacks: Vec<Vec<char>>,
+    stacks: Vec<Vec<u8>>,
     instructions: Vec<Instruction>,
 }
 
@@ -19,62 +19,78 @@ struct Instruction {
     to: usize,
 }
 
-fn parse(input: &'static str) -> Stack {
-    let mut v = input.split("\n\n");
+fn parse(input: &[u8]) -> Stack {
+    let mut stacks = vec![];
 
-    let mut stack_input = v
-        .next()
-        .unwrap()
-        .lines()
-        .map(|c| c.chars().collect::<Vec<char>>())
-        .rev();
-    let mut stacks: Vec<Vec<char>> = vec![];
+    let mut input = input.splitn(2, |&c| c == b'\n');
+    let mut line = input.next().unwrap();
+    let mut rest = input.next().unwrap();
 
-    let stack_names = stack_input.next().unwrap();
+    while rest[0] != b'\n' {
+        let mut i = 1;
 
-    let containers: Vec<Vec<char>> = stack_input.collect();
-
-    for (i, v) in stack_names.into_iter().enumerate() {
-        if v == ' ' {
-            continue;
-        }
-        let v: usize = (v as u8 - b'0') as usize;
-
-        if stacks.len() <= v - 1 {
+        while (3 * (i - 1) + i) < line.len() {
+            if stacks.len() < i {
                 stacks.push(vec![]);
             }
 
-        for container in containers.iter() {
-            if container[i] == ' ' {
-                continue;
-            }
-            stacks[v - 1].push(container[i]);
-        }
+            if (b'A'..=b'Z').contains(&line[3 * (i - 1) + i]) {
+                stacks[i - 1].push(line[3 * (i - 1) + i]);
             }
 
-    let instructions: Vec<Instruction> = v
-        .next()
-        .unwrap()
-        .lines()
-        .map(|line: &str| {
-            let line: String = line
-                .chars()
-                .filter(|c| c.is_numeric() | c.is_whitespace())
+            i += 1;
+        }
+
+        let mut temp = rest.splitn(2, |&c| c == b'\n');
+        line = temp.next().unwrap();
+        rest = temp.next().unwrap();
+    }
+    rest = &rest[1..];
+    let stacks: Vec<Vec<u8>> = stacks
+        .into_iter()
+        .map(|c| c.into_iter().rev().collect())
         .collect();
 
-            let numbers: Vec<u8> = line
-                .split(' ')
+    let mut input = rest.splitn(2, |&c| c == b'\n');
+    let mut line = input.next();
+    let mut rest = input.next();
+
+    let mut instructions = vec![];
+
+    while let Some(l) = line {
+        let l: Vec<u8> = l
+            .iter()
+            .filter(|&c| (b'0'..=b'9').contains(c) || c == &b' ')
+            .cloned()
+            .collect();
+
+        if l.is_empty() {
+            break;
+        }
+
+        let numbers: Vec<u8> = l
+            .split(|&c| c == b' ')
             .filter(|c| !c.is_empty())
-                .map(|c| c.parse::<u8>().unwrap())
+            .map(|c| {
+                c.get(1)
+                    .map_or(c[0] - b'0', |a| (c[0] - b'0') * 10 + a - b'0')
+            })
             .collect();
 
-            Instruction {
+        instructions.push(Instruction {
             count: numbers[0] as usize,
             from: numbers[1] as usize,
             to: numbers[2] as usize,
+        });
+
+        if let Some(r) = rest {
+            let mut input = r.splitn(2, |&c| c == b'\n');
+            line = input.next();
+            rest = input.next();
+        } else {
+            break;
+        }
     }
-        })
-        .collect();
 
     Stack {
         instructions,
@@ -95,7 +111,7 @@ fn solution(mut input: Stack) -> String {
     for ins in input.instructions {
         let l = input.stacks[ins.from - 1].len();
 
-        let crates: Vec<char> = input.stacks[ins.from - 1]
+        let crates: Vec<u8> = input.stacks[ins.from - 1]
             .drain(l.saturating_sub(ins.count)..l)
             .collect();
 
@@ -109,6 +125,7 @@ fn solution(mut input: Stack) -> String {
         .into_iter()
         .filter(|c| !c.is_empty())
         .map(|c| *c.last().unwrap())
+        .map(|c| c as char)
         .collect()
 }