Day five

day-05-rust/src/common.rs

@@ -0,0 +1,60 @@
+use std::collections::HashMap;
+use std::io::{Bytes, Read};
+use std::iter::Peekable;
+use crate::common;
+
+pub type Number = i32;
+
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
+pub struct Rule {
+    pub first: Number,
+    pub second: Number,
+}
+
+pub fn read_rules<R: Read>(mut input: &mut Peekable<Bytes<R>>) -> HashMap<Number, Vec<Rule>> {
+    let mut rules_by_number = HashMap::<Number, Vec<Rule>>::new();
+
+    while let Some(Ok(ch)) = input.peek() {
+        if ch == &b'\n' {
+            input.next();
+            break;
+        }
+        let first = common::read_number(&mut input);
+        input.next();
+        let second = common::read_number(&mut input);
+        input.next();
+
+        let rule = Rule { first, second };
+        rules_by_number
+            .entry(rule.first)
+            .or_default()
+            .push(rule.clone());
+        rules_by_number.entry(rule.second).or_default().push(rule);
+    }
+    rules_by_number
+}
+
+pub fn read_number_list<R: Read>(mut input: &mut Peekable<Bytes<R>>) -> Vec<Number> {
+    let mut numbers = Vec::<Number>::new();
+
+    while let Some(Ok(ch)) = input.peek() {
+        if ch == &b'\n' {
+            break;
+        } else if ch == &b',' {
+            input.next();
+            continue;
+        }
+        let number = common::read_number(&mut input);
+        numbers.push(number);
+    }
+    numbers
+}
+
+pub fn read_number<R: Read>(input: &mut Peekable<Bytes<R>>) -> Number {
+    let mut number: Number = 0;
+    while let Some(Ok(b'0'..=b'9')) = input.peek() {
+        number *= 10;
+        number += (input.next().unwrap().unwrap() - b'0') as Number;
+    }
+    number
+}