Add day01, 2020

2 files changed, 80 insertions, 0 deletions

diff --git a/2020/rust/day01/Cargo.toml b/2020/rust/day01/Cargo.toml
new file mode 100644
index 0000000..674217d
--- /dev/null
+++ b/2020/rust/day01/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day01"
+version = "0.1.0"
+authors = ["cos <cos>"]
+edition = "2018"
+
+[dependencies]
+anyhow = "1.0"
diff --git a/2020/rust/day01/src/main.rs b/2020/rust/day01/src/main.rs
new file mode 100644
index 0000000..38f25d2
--- /dev/null
+++ b/2020/rust/day01/src/main.rs
@@ -0,0 +1,72 @@
+use anyhow::Result;
+use std::env::args;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+use std::path::Path;
+
+const SUM: usize = 2020;
+
+fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<usize>> {
+    let f = File::open(filename)?;
+    let reader = BufReader::new(f);
+
+    let values = reader.lines()
+        .map(|v| v.unwrap().parse::<usize>().unwrap()).collect();
+
+    Ok(values)
+}
+
+fn part1(input: &[usize]) -> Option<usize> {
+    for first in input {
+        for second in input {
+            if first + second == SUM {
+                return Some(first * second);
+            }
+        }
+    }
+
+    None
+}
+
+fn part2(input: &[usize]) -> Option<usize> {
+    for first in input {
+        for second in input {
+            for third in input {
+                if first + second + third == SUM {
+                    return Some(first * second * third);
+                }
+            }
+        }
+    }
+
+    None
+}
+
+fn main() {
+    let filename = match args().nth(1) {
+        Some(f) => f,
+        None => {
+            eprintln!("Missing input filename");
+            std::process::exit(1);
+        },
+    };
+    match  read_input(filename) {
+        Ok(input) => {
+            match part1(&input) {
+                Some(solution) => println!("Part1, product found to be: {}", solution),
+                None => {
+                    eprintln!("Part1, no solution found");
+                    std::process::exit(1);
+                }
+            };
+            match part2(&input) {
+                Some(solution) => println!("Part2, product found to be: {}", solution),
+                None => {
+                    eprintln!("Part2, no solution found");
+                    std::process::exit(1);
+                }
+            };
+        },
+        Err(err) => eprintln!("Could not read input: {}", err),
+    }
+}