First day of 2021, done in Rust

.gitignore

@@ -1 +1,3 @@
 **/.idea
+**/target
+

2021/Day 1/rust_solution/Cargo.lock

@@ -0,0 +1,5 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "rust_solution"
+version = "0.1.0"

2021/Day 1/rust_solution/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "rust_solution"
+version = "0.1.0"
+authors = ["Teo-CD"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2021/Day 1/rust_solution/src/main.rs

@@ -0,0 +1,38 @@
+use std::fs;
+
+fn first_puzzle(input: &String) {
+    // Go through each line and subtract it to the previous one, keeping only the positive results
+    // and counting them, knowing that the first diff is invalid.
+    let count = input.lines().scan(0, |current, line| {
+        let previous = *current;
+        *current = line.parse::<i32>().unwrap();
+        Some(*current - previous)}).filter(|diff| diff.is_positive()).count() - 1;
+
+    println!("Count of single increases : {}", count);
+}
+
+fn second_puzzle(input: &String) {
+    let count = input.lines().scan([0; 4], |sliding_window: &mut [i32; 4], line|{
+        let place = sliding_window[3];
+        sliding_window[(place % 3) as usize] = line.parse::<i32>().unwrap();
+        sliding_window[3] = place + 1;
+
+        if sliding_window[3] < 3 {
+            Some(-1)
+        } else {
+            Some(sliding_window[0..3].iter().sum::<i32>())
+        }
+    }).filter(|sum| !sum.is_negative()).scan(0, |current, sum| {
+        let previous = *current;
+        *current = sum;
+        Some(*current - previous)}).filter(|diff| diff.is_positive()).count() - 1;
+
+    println!("Count of triple sums increasing : {}", count);
+}
+
+fn main() {
+    let contents = fs::read_to_string("../input.txt").expect("Could not open file.");
+    first_puzzle(&contents);
+    second_puzzle(&contents);
+    0;
+}

README.md

@@ -5,4 +5,9 @@ The directory structure is simple : `year/day`, each day containing the input fi
 
 ## Depencies
 
-Only Python3 for now !
+2020:  
+ - Python3
+
+2021:  
+ - Rust (Cargo)
+