Day 1

01/part2.rs

@@ -0,0 +1,45 @@
+use std::collections::HashSet;
+use std::error::Error;
+use std::fs::File;
+use std::io::BufReader;
+use std::io::SeekFrom;
+use std::io::prelude::*;
+
+fn main() -> std::io::Result<()> {
+    let mut file = match File::open("input") {
+        // The `description` method of `io::Error` returns a string that describes the error
+        Err(why) => panic!("couldn't open input: {}", Error::description(&why)),
+        Ok(file) => file,
+    };
+
+    let mut repeat = true;
+    let mut total: i128 = 0;
+    let mut seen = HashSet::<i128>::new();
+    seen.insert(0);
+
+    while repeat {
+        file.seek(SeekFrom::Start(0));
+        let reader = BufReader::new(&file);
+        let lines = reader.lines();
+
+        for result in lines {
+            let l = result.unwrap();
+            let offset:i128 = i128::from_str_radix(&l, 10).unwrap();
+
+            total = total + offset;
+            println!("{} => {}", offset, total);
+
+            if seen.contains(&total) {
+                println!("seen {} before", total);
+                repeat = false;
+                break;
+            }
+
+            seen.insert(total);
+       }
+   }
+
+    println!("{}", total);
+
+    Ok(())
+}