day7: complete solution

7/Cargo.lock

@@ -0,0 +1,25 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day7"
+version = "0.1.0"
+dependencies = [
+ "itertools",
+]
+
+[[package]]
+name = "either"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
+
+[[package]]
+name = "itertools"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
+dependencies = [
+ "either",
+]

7/Cargo.toml

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+[package]
+name = "day7"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+itertools = "0.13.0"

7/src/main.rs

@@ -0,0 +1,169 @@
+use std::fs::File;
+use std::io::{BufRead, BufReader, Lines};
+use std::time::{Duration, Instant};
+
+use itertools::Itertools;
+
+// 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));
+}
+
+#[derive(Debug)]
+struct Calibration {
+    result: u64,
+    numbers: Vec<u64>,
+}
+
+impl From<&str> for Calibration {
+    fn from(value: &str) -> Self {
+        let (result, rest) = value.splitn(2, ':').next_tuple().unwrap();
+        Self {
+            result: result.parse().unwrap(),
+            numbers: rest.split_ascii_whitespace().map(|s| s.parse().unwrap()).collect(),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct Calibrations {
+    cals: Vec<Calibration>,
+}
+
+#[derive(Debug)]
+enum Operator {
+    Add,
+    Multiply,
+    Concatenate,
+}
+
+impl Operator {
+    fn exec(&self, a: u64, b: u64) -> u64 {
+        match self {
+            Operator::Add => a + b,
+            Operator::Multiply => a * b,
+            Operator::Concatenate => u64::pow(10, b.to_string().len() as u32) * a + b,
+        }
+    }
+}
+
+impl<T: BufRead> From<Lines<T>> for Calibrations {
+    fn from(input: Lines<T>) -> Self {
+        let mut cals = Vec::new();
+        for line in input.map(|l| l.unwrap()) {
+            cals.push(line.as_str().into());
+        }
+        Self { cals }
+    }
+}
+
+// PROBLEM 1 solution
+
+fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
+    let cals = Calibrations::from(input);
+    // println!("{:?}", cals);
+    let mut sum = 0;
+
+    let operators = [Operator::Add, Operator::Multiply];
+
+    for cal in &cals.cals {
+        let n_opers = cal.numbers.len() - 1;
+        // println!("CAL: {:?} (opers: {})", cal, n_opers);
+        for oper_set in std::iter::repeat_n(operators.iter(), n_opers).multi_cartesian_product() {
+            // println!("operator set: {:?}", oper_set);
+            let mut accum = cal.numbers[0];
+            for (i, oper) in oper_set.iter().enumerate() {
+                // println!("Testing {} {:?} {}", accum, oper, cal.numbers[i+1]);
+                accum = oper.exec(accum, cal.numbers[i + 1]);
+            }
+            if accum == cal.result {
+                sum += cal.result;
+                // println!("Matched!");
+                break;
+            }
+        }
+        // println!("NO MATCHES");
+    }
+    sum
+}
+
+// PROBLEM 2 solution
+fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
+    let cals = Calibrations::from(input);
+    let mut sum = 0;
+    let operators = [Operator::Add, Operator::Multiply, Operator::Concatenate];
+    for cal in &cals.cals {
+        let n_opers = cal.numbers.len() - 1;
+        // println!("CAL: {:?} (opers: {})", cal, n_opers);
+        for oper_set in std::iter::repeat_n(operators.iter(), n_opers).multi_cartesian_product() {
+            // println!("operator set: {:?}", oper_set);
+            let mut accum = cal.numbers[0];
+            for (i, oper) in oper_set.iter().enumerate() {
+                // println!("Testing {} {:?} {}", accum, oper, cal.numbers[i+1]);
+                accum = oper.exec(accum, cal.numbers[i + 1]);
+            }
+            if accum == cal.result {
+                sum += cal.result;
+                // println!("Matched!");
+                break;
+            }
+        }
+        // println!("NO MATCHES");
+    }
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+    use std::io::Cursor;
+
+    const EXAMPLE: &str = &"190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20";
+
+    #[test]
+    fn problem1_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem1(c.lines()), 3749);
+    }
+
+    #[test]
+    fn problem2_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem2(c.lines()), 11387);
+    }
+}