Implement 2025 - Day 2 - Part 2

2025/01.rs

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+---cargo
+---
+
+static CONTENT: &'static str = include_str!("./inputs/01_1.txt");
+
+#[derive(Debug)]
+enum Direction {
+    Left,
+    Right,
+}
+
+#[derive(Debug)]
+struct Rotation {
+    direction: Direction,
+    amount: usize,
+}
+
+fn main() {
+    let rotations: Vec<Rotation> = CONTENT.lines().map(|l| l.trim()).filter(|l| !l.is_empty()).map(|l| {
+        let (direction, raw_amount) = l.split_at(1);
+
+        let direction = match direction {
+            "L" => Direction::Left,
+            "R" => Direction::Right,
+            other => unreachable!("Unknown Direction: {:?}", other),
+        };
+
+        let amount = match raw_amount.parse::<usize>() {
+            Ok(a) => a,
+            Err(e) => unreachable!("Invalid Amount ({:?}): {:?}", raw_amount, e),
+        };
+
+        Rotation {
+            direction,
+            amount,
+        }
+    }).collect();
+
+    println!("Rotations: {:#?}", rotations);
+
+    let mut count: usize = 0;
+
+    let mut state: isize = 50;
+    for rot in rotations.iter() {
+        if rot.amount >= 100 {
+            count += rot.amount / 100;
+        }
+
+        let amount = rot.amount % 100;
+        if amount == 0 {
+            continue;
+        }
+
+        match rot.direction {
+            Direction::Left => {
+                if state != 0 && amount > state as usize {
+                    count += 1;
+                }
+
+                state = state.strict_sub_unsigned(amount);
+                state = state.strict_rem_euclid(100);
+
+                if state == 0 {
+                    count += 1;
+                }
+            }
+            Direction::Right => {
+                state = state.strict_add_unsigned(amount);
+                if state >= 100 {
+                    count += 1;
+                }
+
+                state = state.strict_rem_euclid(100);
+            }
+        };
+
+        println!("Applying {:?} => {} ({})", rot, state, count);
+    }
+
+    println!("Result: {}", count);
+}

2025/02.rs

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+---cargo
+---
+
+static CONTENT: &'static str = include_str!("./inputs/02_1.txt");
+
+fn main() {
+    let ranges: Vec<_> = CONTENT.split(',').map(|l| l.trim()).filter(|l| !l.is_empty()).map(|l| {
+        let (raw_start, raw_end) = l.split_once('-').unwrap();
+        let start: usize = raw_start.parse().unwrap();
+        let end: usize = raw_end.parse().unwrap();
+
+        start..=end
+    }).collect();
+
+    println!("Ranges: {:?}", ranges);
+
+    let mut result = 0;
+    for r in ranges.iter() {
+        for v in r.clone() {
+            let v_len = v.ilog10() + 1;
+            
+            let mut iter = (1..=v_len/2).filter_map(|len| {
+                if v_len % len != 0 {
+                    return None;
+                }
+
+                let mut seqs = (0..v_len/len).map(|i| {
+                    let offset = 10_usize.pow(i*len);
+                    let mask = 10_usize.pow(len);
+
+                    (v/offset) % mask
+                });
+
+                let first = match seqs.next() {
+                    Some(f) => f,
+                    None => return None,
+                };
+
+                let invalid = seqs.all(|s| s == first);
+                invalid.then_some((first, len, v_len/len))
+            });
+
+            let first = iter.next();
+            if first.is_some() {
+                println!("{} - {:?}", v, first);
+                result += v;
+            }  
+        }
+    }
+
+    println!("Result: {}", result);
+}

2025/inputs/01_example.txt

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+L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82

2025/inputs/02_1.txt

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+17330-35281,9967849351-9967954114,880610-895941,942-1466,117855-209809,9427633930-9427769294,1-14,311209-533855,53851-100089,104-215,33317911-33385573,42384572-42481566,43-81,87864705-87898981,258952-303177,451399530-451565394,6464564339-6464748782,1493-2439,9941196-10054232,2994-8275,6275169-6423883,20-41,384-896,2525238272-2525279908,8884-16221,968909030-969019005,686256-831649,942986-986697,1437387916-1437426347,8897636-9031809,16048379-16225280

2025/inputs/02_example.txt

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+11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124

README.md

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+# Advent of Code