2022 Day 25 Part 1

2022/src/bin/day25.rs

@@ -0,0 +1,59 @@
+use std::collections::VecDeque;
+
+const INPUT: &str = include_str!("../../input/day25.txt");
+
+fn main() {
+    println!("{}", part1(INPUT));
+}
+
+fn part1(input: &str) -> String {
+    let mut sum = 0;
+    for line in input.lines() {
+        let mut num: i64 = 0;
+        for (i, digit) in line.chars().rev().enumerate() {
+            let val = match digit {
+                '=' => -2,
+                '-' => -1,
+                '0' => 0,
+                '1' => 1,
+                '2' => 2,
+                other => panic!("{:?}", other),
+            };
+
+            num += 5_i64.pow(i.try_into().unwrap()) * val;
+        }
+        sum += num;
+    }
+    snafu(sum)
+}
+
+fn snafu(mut n: i64) -> String {
+    assert!(n > 0);
+
+    let mut digits: VecDeque<i64> = VecDeque::new();
+
+    while n > 0 {
+        match n % 5 {
+            3 => digits.push_front(-2),
+            4 => digits.push_front(-1),
+            0 => digits.push_front(0),
+            1 => digits.push_front(1),
+            2 => digits.push_front(2),
+            other => panic!("{:?}", other),
+        };
+        n -= digits[0];
+        n /= 5;
+    }
+
+    digits
+        .iter()
+        .map(|digit| match digit {
+            -2 => '=',
+            -1 => '-',
+            0 => '0',
+            1 => '1',
+            2 => '2',
+            other => panic!("{:?}", other),
+        })
+        .collect()
+}