Rust for 2a

2018/02/rust/checksum/Cargo.toml

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+[package]
+name = "checksum"
+version = "0.1.0"
+authors = ["Tom <[email protected]>"]
+edition = "2018"
+
+[dependencies]

2018/02/rust/checksum/src/main.rs

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+use std::io::{self, BufRead, BufReader};
+use std::fs::File;
+
+fn main() -> Try<()> {
+    let file = File::open("../../input/input.txt")?;
+    let mut count2 = 0;
+    let mut count3 = 0;
+    for line in BufReader::new(file).lines() {
+        // Count chars.
+        let mut counts = [0; 256];
+        for c in line?.bytes() {
+            counts[c as usize] += 1;
+        }
+        // Find 2s and 3s.
+        count2 += counts.iter().any(|count| *count == 2) as i32;
+        count3 += counts.iter().any(|count| *count == 3) as i32;
+    }
+    println!("{}", count2 * count3);
+    Ok(())
+}
+
+#[derive(Debug)]
+pub struct Err {
+    pub message: String,
+}
+
+type Try<Value> = Result<Value, Err>;
+
+impl From<io::Error> for Err {
+    fn from(_: io::Error) -> Err {
+        Err{message: "io error".to_string()}
+    }
+}
+
+impl From<std::num::ParseIntError> for Err {
+    fn from(_: std::num::ParseIntError) -> Err {
+        Err{message: "parse int error".to_string()}
+    }
+}