2017: Day 01

2017/01/src/main.rs

@@ -0,0 +1,62 @@
+use std::env;
+use std::fs;
+use std::io::Read;
+
+
+fn captcha(input: &str, step: usize) -> u32 {
+    let digits = input
+        .chars()
+        .flat_map(|c| c.to_digit(10))
+        .collect::<Vec<_>>();
+
+    let len = digits.len();
+
+    digits
+        .iter()
+        .enumerate()
+        .filter(|&(i, digit)| *digit == digits[(i + step) % len])
+        .map(|(_, digit)| digit)
+        .sum::<u32>()
+}
+
+fn main() {
+    let file_name = env::args().nth(1).expect("path to input file");
+
+    let mut input = String::new();
+
+    fs::File::open(file_name)
+        .and_then(|mut file| file.read_to_string(&mut input))
+        .expect("faild to read file");
+
+    for line in input
+        .lines()
+        .map(|line| line.trim())
+        .filter(|line| !line.is_empty())
+    {
+        println!("part-01: {}", captcha(line, 1));
+        println!("part-02: {}", captcha(line, line.len() / 2));
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part_1() {
+        assert_eq!(captcha("1122", 1), 3);
+        assert_eq!(captcha("1111", 1), 4);
+        assert_eq!(captcha("1234", 1), 0);
+        assert_eq!(captcha("91212129", 1), 9);
+    }
+
+    #[test]
+    fn part_2() {
+        assert_eq!(captcha("1212", 2), 6);
+        assert_eq!(captcha("1221", 2), 0);
+        assert_eq!(captcha("123425", 3), 4);
+        assert_eq!(captcha("123123", 3), 12);
+        assert_eq!(captcha("12131415", 4), 4);
+    }
+}