First 2 days and a half

.gitignore

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+target
+*-input.txt

Cargo.lock

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

Cargo.toml

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+[package]
+name = "aoc"
+version = "0.1.0"
+authors = ["Vladan Popovic <vladan.popovic@ericsson.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/day_one.rs

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+fn fuel_for(mass: u64) -> u64 {
+    (mass / 3).saturating_sub(2)
+}
+
+fn total_fuel(mass: u64) -> u64 {
+    std::iter::successors(Some(fuel_for(mass)), |&fuel| Some(fuel_for(fuel)))
+        .take_while(|&fuel| fuel > 0)
+        .sum()
+}
+
+pub fn main(masses: Vec<u64>) {
+    let total: u64 = masses.into_iter().map(total_fuel).sum();
+    println!("Fuel needed for bringing Santa home is: {}", total);
+}
+
+#[test]
+fn test_part1() {
+    assert_eq!(fuel_for(12), 2);
+    assert_eq!(fuel_for(14), 2);
+    assert_eq!(fuel_for(1969), 654);
+    assert_eq!(fuel_for(100756), 33583);
+}
+
+#[test]
+fn test_part2() {
+    assert_eq!(total_fuel(14), 2);
+    assert_eq!(total_fuel(1969), 966);
+    assert_eq!(total_fuel(100756), 50346);
+}

src/day_three.rs

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+use std::collections::BTreeSet;
+use std::fs::File;
+use std::io::{self, BufRead, BufReader};
+use std::iter::{repeat, successors};
+
+fn next(c: (i32, i32), direction: &str) -> (i32, i32) {
+    match direction {
+        "R" => (c.0 + 1, c.1),
+        "L" => (c.0 - 1, c.1),
+        "U" => (c.0, c.1 + 1),
+        "D" => (c.0, c.1 - 1),
+        _ => panic!("Wrong direction format!"),
+    }
+}
+
+fn direction_length(entry: String) -> (String, usize) {
+    /// Creates a (direction, length) pair to later produce a string
+    /// on a direction with the given length. E.g. given "R10" the output of
+    (
+        entry.chars().nth(0).unwrap().to_string(),
+        entry[1..].parse().unwrap(),
+    )
+}
+
+fn to_coordinates(entries: Vec<String>) -> BTreeSet<(i32, i32)> {
+    let mut wire = BTreeSet::new();
+
+    let mut it = entries
+        .into_iter()
+        .map(direction_length)
+        .flat_map(|(direction, length)| repeat(direction).take(length));
+
+    successors(
+        it.next()
+            .map(|direction| (next((0, 0), direction.as_ref()))),
+        |c| it.next().map(|direction| (next(*c, direction.as_ref()))),
+    )
+    .for_each(|c| {
+        wire.insert(c);
+    });
+
+    wire
+}
+
+fn distance(position: (i32, i32)) -> i32 {
+    position.0.abs() + position.1.abs()
+}
+
+pub fn main() -> io::Result<()> {
+    let f = BufReader::new(File::open("day3-input.txt")?);
+    let entries: Vec<BTreeSet<(i32, i32)>> = f
+        .lines()
+        .map(|line| line.unwrap().split(",").map(String::from).collect())
+        .map(to_coordinates)
+        .collect();
+
+    let closest: Option<i32> = entries[0]
+        .intersection(&entries[1])
+        .cloned()
+        .map(distance)
+        .min();
+    println!("{:?}", closest);
+
+    Ok(())
+}
+
+#[test]
+fn test_coordinates_for_entry() {
+    let mut expected: BTreeSet<(i32, i32)> = BTreeSet::new();
+    for i in 1..11 {
+        expected.insert((i, 0));
+    }
+    assert_eq!(to_coordinates(vec!["R10".to_owned()]), expected);
+
+    expected = BTreeSet::new();
+    expected.insert((1, 0));
+    expected.insert((2, 0));
+    expected.insert((2, 1));
+    expected.insert((2, 2));
+    let input = "R2,U2".to_owned().split(",").map(String::from).collect();
+    assert_eq!(to_coordinates(input), expected);
+}

src/day_two.rs

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+use std;
+
+fn compute_intcode(p: &mut Vec<usize>) -> Vec<usize> {
+    for idx in (0..(p.len())).step_by(4) {
+        match p[idx] {
+            1 => {
+                let left = p[idx + 1];
+                let right = p[idx + 2];
+                let res = p[idx + 3];
+                p[res] = p[left] + p[right];
+            }
+            2 => {
+                let left = p[idx + 1];
+                let right = p[idx + 2];
+                let res = p[idx + 3];
+                p[res] = p[left] * p[right];
+            }
+            99 => break,
+            _ => panic!("Something went wrong!"),
+        }
+    }
+    p.to_vec()
+}
+
+pub fn part_one() {
+    let mut input: Vec<usize> = std::include_str!("../day2-input.txt")
+        .trim()
+        .split(",")
+        .map(|x| x.parse().unwrap())
+        .collect();
+
+    input[1] = 12;
+    input[2] = 2;
+
+    println!("Intcode [0] is: {}", compute_intcode(&mut input)[0]);
+}
+
+pub fn part_two() {
+    let mut input: Vec<usize> = std::include_str!("../day2-input.txt")
+        .trim()
+        .split(",")
+        .map(|x| x.parse().unwrap())
+        .collect();
+
+    input[1] = 0;
+    input[2] = 0;
+
+    let lookup_num = 19690720;
+    let mut found = false;
+
+    for i in 0..99 {
+        input[1] = i;
+        for j in 0..99 {
+            input[2] = j;
+            let mut input_guess = input.clone();
+            let computed = compute_intcode(&mut input_guess);
+
+            found = computed[0] == lookup_num;
+
+            if found {
+                let (noun, verb) = (computed[1], computed[2]);
+                println!(
+                    "100 * noun({}) + verb({}) = {}",
+                    noun,
+                    verb,
+                    100 * noun + verb
+                );
+                break;
+            }
+        }
+        if found {
+            break;
+        }
+    }
+}
+
+#[test]
+fn test_part_one() {
+    assert_eq!(
+        compute_intcode(&mut vec!(1, 0, 0, 0, 99)),
+        vec!(2, 0, 0, 0, 99)
+    );
+    assert_eq!(
+        compute_intcode(&mut vec!(2, 3, 0, 3, 99)),
+        vec!(2, 3, 0, 6, 99)
+    );
+    assert_eq!(
+        compute_intcode(&mut vec!(2, 4, 4, 5, 99, 0)),
+        vec!(2, 4, 4, 5, 99, 9801)
+    );
+    assert_eq!(
+        compute_intcode(&mut vec!(1, 1, 1, 4, 99, 5, 6, 0, 99)),
+        vec!(30, 1, 1, 4, 2, 5, 6, 0, 99)
+    );
+}

src/main.rs

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+mod day_one;
+mod day_three;
+mod day_two;
+
+use std::fs::File;
+use std::io::{self, BufRead, BufReader};
+
+fn main() -> io::Result<()> {
+    let f = BufReader::new(File::open("day1-input.txt")?);
+    let masses: Vec<u64> = f
+        .lines()
+        .map(|line| line.unwrap().parse().unwrap())
+        .collect();
+    day_one::main(masses);
+
+    day_two::part_one();
+    day_two::part_two();
+
+    day_three::main()?;
+
+    Ok(())
+}