2022 - Day 25 [Merry Christmas!]

2022/src/bin/day25.rs

@@ -0,0 +1,97 @@
+#![feature(test)]
+use anyhow::Result;
+use aoc::Solver;
+
+// -- Runners --
+fn main() -> Result<()> {
+    Day::solve()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_test1() -> Result<()> {
+        Day::test(Day::part1, "test-1", "2=-1=0".to_owned())
+    }
+    #[test]
+    fn part1_solution() -> Result<()> {
+        Day::test(Day::part1, "input", "2-20=01--0=0=0=2-120".to_owned())
+    }
+
+    // Benchmarks
+    extern crate test;
+    #[bench]
+    #[ignore]
+    fn part1_bench(b: &mut test::Bencher) {
+        Day::benchmark(Day::part1, b)
+    }
+    #[bench]
+    #[ignore]
+    fn part2_bench(b: &mut test::Bencher) {
+        Day::benchmark(Day::part2, b)
+    }
+}
+
+// -- Solution --
+pub struct Day;
+impl aoc::Solver for Day {
+    type Output1 = String;
+    type Output2 = String;
+
+    fn day() -> u8 {
+        25
+    }
+
+    fn part1(input: &str) -> Self::Output1 {
+        let mut sum: isize = input
+            .trim()
+            .lines()
+            .map(|line| {
+                line.chars().rev().enumerate().fold(0, |acc, (idx, c)| {
+                    let num = match c {
+                        '2' => 2,
+                        '1' => 1,
+                        '0' => 0,
+                        '-' => -1,
+                        '=' => -2,
+                        _ => panic!("Invalid number!"),
+                    };
+
+                    acc + num * 5_isize.pow(idx as u32)
+                })
+            }).sum();
+
+        let mut result = String::new();
+        while sum > 0 {
+            let mut carry = 0;
+            let rem = sum % 5;
+            match rem {
+                0 => result += "0",
+                1 => result += "1",
+                2 => result += "2",
+                3 => {
+                    result += "=";
+                    carry += 1;
+                },
+                4 => {
+                    result += "-";
+                    carry += 1;
+                },
+                _ => unreachable!("Number is mod 5 so should always be 0..=4"),
+            }
+
+            sum = sum/5 + carry;
+        }
+        // Reverse the string, since we construct it the wrong way around
+        result = result.chars().rev().collect();
+
+        result
+    }
+
+    fn part2(_input: &str) -> Self::Output2 {
+        // There is no part 2!
+        "Merry Christmas!".to_owned()
+    }
+}