Day five

day-05-rust/src/task1.rs

@@ -0,0 +1,45 @@
+use crate::common::{read_number_list, read_rules, Number};
+use std::collections::HashSet;
+use std::io::Read;
+use std::ops::Rem;
+
+pub fn run<R: Read>(read: R) {
+    let mut input = read.bytes().peekable();
+
+    let rules_by_number = read_rules(&mut input);
+
+    let mut result: Number = 0;
+
+    while let Some(Ok(ch)) = input.peek() {
+        if ch == &b'\n' {
+            input.next();
+            continue;
+        }
+
+        let numbers = read_number_list(&mut input);
+
+        let rules = numbers
+            .iter()
+            .flat_map(|number| rules_by_number.get(number))
+            .flatten()
+            .filter(|rule| numbers.contains(&rule.first) && numbers.contains(&rule.second))
+            .collect::<HashSet<_>>();
+
+        if rules.iter().all(|rule| {
+            numbers
+                .iter()
+                .position(|number| *number == rule.first)
+                .zip(numbers.iter().position(|number| *number == rule.second))
+                .map(|(first_index, second_index)| first_index < second_index)
+                .unwrap_or(false)
+        }) {
+            if numbers.len().rem(2) == 1 {
+                result += numbers[numbers.len() / 2];
+            } else {
+                eprintln!("Length of numbers is not odd!")
+            }
+        }
+    }
+
+    println!("Result {}", result);
+}