first commit

README.md

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+# Advent of code 2021
+
+This repo contains my solutions for advent of code 2021 :)
+
+I will solve all of the problems with Rust, trying to take a functional approach for the problems

day1/.gitignore

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+/target

day1/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day1"
+version = "0.1.0"

day1/Cargo.toml

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+[package]
+name = "day1"
+version = "0.1.0"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day1/src/main.rs

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+use std::fs::File;
+use std::io::{self, BufRead};
+use std::io::{BufReader, Lines, Result};
+use std::iter::Iterator;
+use std::path::Path;
+
+const INPUT_PATH: &'static str = "./input.txt";
+
+fn main() -> Result<()> {
+    let depths = read_depths(INPUT_PATH)?;
+    // First puzzle
+    let increases = count_increases(&depths);
+    println!("First puzzle {0}", increases);
+    // Second puzzle
+    let sliding_window_sums = calculate_sliding_window_sums(&depths, 3);
+    let increases = count_increases(&sliding_window_sums);
+    println!("Second puzzle {0}", increases);
+    Ok(())
+}
+
+fn calculate_sliding_window_sums(depths: &[i32], size: usize) -> Vec<i32> {
+    let mut sums = vec![];
+    for i in 0..=depths.len() - size {
+        let window = &depths[i..i + size];
+        let sum = window.into_iter().fold(0, |a, &b| a + b);
+        sums.push(sum)
+    }
+    sums
+}
+
+fn count_increases(nums: &[i32]) -> i32 {
+    // Map an iterator of nums to [last_num, counter]
+    let [_, counter] = nums.iter().fold([0, -1], |[prev, counter], &curr| {
+        [curr, counter + if curr > prev { 1 } else { 0 }]
+    });
+    counter
+}
+
+fn read_depths(file_path: &str) -> Result<Vec<i32>> {
+    read_lines(file_path).map(lines_to_depths)
+}
+
+fn lines_to_depths(lines: Lines<BufReader<File>>) -> Vec<i32> {
+    lines
+        .filter_map(|line| line.ok().map(line_to_depth))
+        .collect()
+}
+
+fn line_to_depth(line: String) -> i32 {
+    line.parse::<i32>().unwrap()
+}
+
+// The output is wrapped in a Result to allow matching on errors
+// Returns an Iterator to the Reader of the lines of the file.
+fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
+where
+    P: AsRef<Path>,
+{
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}