Day five

day-05-rust/.gitignore

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+target/

day-05-rust/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day-05-rust"
+version = "0.1.0"

day-05-rust/Cargo.toml

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+[package]
+name = "day-05-rust"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

day-05-rust/src/common.rs

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+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
+}

day-05-rust/src/main.rs

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+mod task1;
+mod task2;
+mod common;
+
+fn main() {
+    let args = std::env::args().collect::<Vec<String>>();
+
+    if args.len() != 3 {
+        eprintln!("Usage: {} <1|2> <input file>", args[0]);
+        std::process::exit(1);
+    }
+
+    match args[1].as_str() {
+        "1" => {
+            task1::run(std::fs::File::open(&args[2]).expect("File not found"));
+        }
+        "2" => {
+            task2::run(std::fs::File::open(&args[2]).expect("File not found"));
+        }
+        _ => eprintln!("Unknown task: {}", args[2]),
+    }
+}

day-05-rust/src/task1.rs

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+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);
+}

day-05-rust/src/task2.rs

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+use crate::common::{read_number_list, read_rules, Number, Rule};
+use std::collections::{HashMap, HashSet};
+use std::io::Read;
+use std::ops::{Not, Rem};
+
+#[derive(Debug, Default, Clone)]
+struct Edges {
+    incoming: HashSet<Rule>,
+    outgoing: HashSet<Rule>,
+}
+
+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)
+        }) {
+            let mut edges_by_nodes = HashMap::<Number, Edges>::new();
+            rules.iter().for_each(|rule| {
+                edges_by_nodes
+                    .entry(rule.first)
+                    .or_default()
+                    .outgoing
+                    .insert((*rule).clone());
+                edges_by_nodes
+                    .entry(rule.second)
+                    .or_default()
+                    .incoming
+                    .insert((*rule).clone());
+            });
+
+            let mut sorted_numbers = Vec::<Number>::with_capacity(numbers.len());
+            while edges_by_nodes.is_empty().not() {
+                if let Some(start_node) = edges_by_nodes
+                    .iter()
+                    .filter(|(_node, edges)| edges.incoming.is_empty())
+                    .next()
+                    .map(|(node, _edges)| *node)
+                {
+                    sorted_numbers.push(start_node);
+                    let edges = edges_by_nodes.remove(&start_node).unwrap();
+                    for outgoing in edges.outgoing {
+                        if let Some(target_edges) = edges_by_nodes.get_mut(&outgoing.second) {
+                            target_edges.incoming.remove(&outgoing);
+                        }
+                    }
+                } else {
+                    eprintln!("Inconsistent situation");
+                    break;
+                }
+            }
+            
+            if sorted_numbers.len().rem(2) == 1 {
+                result += sorted_numbers[sorted_numbers.len() / 2];
+            } else {
+                eprintln!("Line doesn't have odd length")
+            }
+        }
+    }
+
+    println!("Result {}", result);
+}