day01

.gitignore

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+/target
+Cargo.lock

Cargo.toml

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+[package]
+name = "aoc2020"
+version = "0.1.0"
+authors = ["Stefan Schwarz <ssz@bitsbeats.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0"
+
+[[bin]]
+name = "day01"
+path = "src/day01/main.rs"

input01

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src/day01/main.rs

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+use anyhow::Result;
+use std::io::prelude::*;
+use std::io::stdin;
+
+fn main() -> Result<()> {
+    let nums: Vec<i64> = stdin()
+        .lock()
+        .lines()
+        .map(|line| {
+            line.expect("unable to read input")
+                .parse::<i64>()
+                .expect("input is not a number")
+        })
+        .collect();
+    'outer: for a in nums.iter() {
+        for b in nums.iter() {
+            if a + b == 2020 {
+                println!("{} + {} = 2020", a, b);
+                println!("product: {}", a * b);
+                break 'outer;
+            }
+        }
+    }
+    'outer: for a in nums.iter() {
+        for b in nums.iter() {
+            for c in nums.iter() {
+                if a + b + c == 2020 {
+                    println!("{} + {} + {} = 2020", a, b, c);
+                    println!("product: {}", a * b * c);
+                    break 'outer;
+                }
+            }
+        }
+    }
+    Ok(())
+}

src/lib.rs

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+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}