day3: full solution

3/src/main.rs

@@ -0,0 +1,88 @@
+use regex::Regex;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Lines};
+use std::time::{Duration, Instant};
+
+// BOILERPLATE
+type InputIter = Lines<BufReader<File>>;
+
+pub fn get_input() -> InputIter {
+    let f = File::open("input").unwrap();
+    let br = BufReader::new(f);
+    br.lines()
+}
+
+fn duration_format(duration: Duration) -> String {
+    match duration.as_secs_f64() {
+        x if x > 1.0 => format!("{:.3}s", x),
+        x if x > 0.010 => format!("{:.3}ms", x * 1e3),
+        x => format!("{:.3}us", x * 1e6),
+    }
+}
+
+fn main() {
+    let input = get_input();
+    let start = Instant::now();
+    let ans1 = problem1(input);
+    let duration1 = start.elapsed();
+    println!("Problem 1 solution: {} [{}]", ans1, duration_format(duration1));
+
+    let input = get_input();
+    let start = Instant::now();
+    let ans2 = problem2(input);
+    let duration2 = start.elapsed();
+    println!("Problem 2 solution: {} [{}]", ans2, duration_format(duration2));
+    println!("Total duration: {}", duration_format(duration1 + duration2));
+}
+
+// PROBLEM 1 solution
+
+fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
+    let mut sum = 0u64;
+    for line in input.map(|i| i.unwrap()) {
+        let re = Regex::new(r"mul\((\d+),(\d+)\)").unwrap();
+        for m in re.captures_iter(&line) {
+            sum += m[1].parse::<u64>().unwrap() * m[2].parse::<u64>().unwrap();
+        }
+    }
+    sum
+}
+
+// PROBLEM 2 solution
+fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
+    let mut sum = 0u64;
+    let mut do_mul = true;
+    for line in input.map(|i| i.unwrap()) {
+        let re = Regex::new(r"(do\(\)|don't\(\)|mul\((\d+),(\d+)\))").unwrap();
+        for m in re.captures_iter(&line) {
+            match &m[1] {
+                "do()" => do_mul = true,
+                "don't()" => do_mul = false,
+                _ if do_mul => sum += m[2].parse::<u64>().unwrap() * m[3].parse::<u64>().unwrap(),
+                _ => {}
+            }
+        }
+    }
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+    use std::io::Cursor;
+
+    const EXAMPLE1: &str = &"xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))";
+    const EXAMPLE2: &str = &"xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))";
+
+    #[test]
+    fn problem1_example() {
+        let c = Cursor::new(EXAMPLE1);
+        assert_eq!(problem1(c.lines()), 161);
+    }
+
+    #[test]
+    fn problem2_example() {
+        let c = Cursor::new(EXAMPLE2);
+        assert_eq!(problem2(c.lines()), 48);
+    }
+}