day 03

src/bin/03.rs

@@ -0,0 +1,68 @@
+advent_of_code::solution!(3);
+
+fn get_largest_battery(battery: &[u32], start_idx: usize, end_idx: usize) -> Option<(u32, usize)> {
+    let mut largest = battery[start_idx];
+    let mut largest_idx = start_idx;
+    for i in start_idx..=end_idx {
+        if battery[i] > largest {
+            largest = battery[i];
+            largest_idx = i;
+        }
+    }
+    Some((largest, largest_idx))
+}
+
+fn get_joltage(line: &str, desired_digits: u8) -> Option<u64> {
+    let all_values = line.chars().into_iter().map(|c| c.to_digit(10).unwrap()).collect::<Vec<u32>>();
+    // determine the largest joltage by finding the largest battery in the list (excluding the last item) and then the largest battery after that
+    let mut total: u64 = 0;
+    let mut start_idx = 0;
+
+    // print!("Calculating joltage for line: {} -> ", line);
+    for i in 1..=desired_digits {
+        let end_idx = all_values.len() - (1 + desired_digits - i) as usize;
+        // print!("Finding largest between {} and {}", start_idx, end_idx);
+        let (largest, largest_idx) = get_largest_battery(&all_values, start_idx, end_idx).unwrap();
+        // println!(" -> found {}", largest);
+        total = total * 10 + largest as u64;
+        start_idx = largest_idx + 1;
+    }
+    Some(total)
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let mut total: u64 = 0;
+    for line in input.split('\n').filter(|l| !l.is_empty()) {
+        total += get_joltage(line, 2).unwrap();
+    }
+
+    println!("Total: {}", total);
+    Some(total)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let mut total: u64 = 0;
+    for line in input.split('\n').filter(|l| !l.is_empty()) {
+        total += get_joltage(line, 12).unwrap();
+    }
+
+    println!("Total: {}", total);
+    Some(total)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(357));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(3121910778619));
+    }
+}