example.txt

@@ -1,2 +1,33 @@
-Time:      7  15   30
+seeds: 79 14 55 13
-Distance:  9  40  200
+
+seed-to-soil map:
+50 98 2
+52 50 48
+
+soil-to-fertilizer map:
+0 15 37
+37 52 2
+39 0 15
+
+fertilizer-to-water map:
+49 53 8
+0 11 42
+42 0 7
+57 7 4
+
+water-to-light map:
+88 18 7
+18 25 70
+
+light-to-temperature map:
+45 77 23
+81 45 19
+68 64 13
+
+temperature-to-humidity map:
+0 69 1
+1 0 69
+
+humidity-to-location map:
+60 56 37
+56 93 4

input.txt

@@ -1,2 +1,172 @@
-Time:        44     82     69     81
+seeds: 5844012 110899473 1132285750 58870036 986162929 109080640 3089574276 100113624 2693179996 275745330 2090752257 201704169 502075018 396653347 1540050181 277513792 1921754120 26668991 3836386950 66795009
-Distance:   202   1076   1138   1458
+
+seed-to-soil map:
+3547471595 1239929038 174680800
+3052451552 758183681 481745357
+0 1427884524 1775655006
+2844087171 549819300 208364381
+3767989253 4004864866 5194940
+3534196909 1414609838 13274686
+1775655006 114264781 435554519
+4148908402 4010059806 146058894
+2729822390 0 114264781
+3773184193 4156118700 138848596
+2211209525 3203539530 518612865
+3912032789 3767989253 236875613
+
+soil-to-fertilizer map:
+912405184 1056091028 152837752
+194471272 1208928780 200072008
+136115250 240819204 58356022
+3502815281 3536983174 299994001
+2321814552 2458149869 18748048
+3173949445 2623931701 9591555
+394543280 888648379 167442649
+1990258415 3891640206 212931291
+1068754270 54862533 153774684
+1222528954 660792432 186471834
+3340878967 3405750148 131233026
+3472111993 3836977175 30703288
+561985929 299175226 225501956
+2942828492 4104571497 88527954
+874532405 850775600 37872779
+3031356446 3867680463 23959743
+842350418 208637217 32181987
+0 524677182 136115250
+1065242936 847264266 3511334
+2203189706 2339525023 118624846
+1929736108 2563409394 60522307
+3802809282 1847367009 492158014
+1847367009 2790861223 82369099
+2442430445 2873230322 500398047
+3183541000 2633523256 157337967
+3141827666 3373628369 32121779
+787487885 0 54862533
+3055316189 2476897917 86511477
+2340562600 4193099451 101867845
+
+fertilizer-to-water map:
+798315344 439687669 1930292
+1174979421 2966258900 475289790
+439687669 778614573 55925503
+3743699694 3453541232 155280637
+2989334775 1659556189 96021468
+1650269211 3441548690 11992542
+3898980331 3608821869 395986965
+1705125292 2123762646 842496254
+3375514705 1755577657 368184989
+646363825 441617961 94777173
+1662261753 1616692650 42863539
+495613172 627863920 150750653
+2777061135 1174979421 212273640
+741140998 834540076 57174346
+800245636 536395134 91468786
+2547621546 1387253061 229439589
+3085356243 4004808834 290158462
+
+water-to-light map:
+541719462 212840988 165903288
+3437755571 1615831015 672632835
+1051033542 2678450187 510773217
+243353905 378744276 104057369
+1561806759 3801474127 134575711
+707622750 677109833 258560892
+2580483557 1051033542 195631857
+0 935670725 30512917
+347411274 482801645 194308188
+30512917 0 127836567
+2190497220 2288463850 389986337
+3068589955 1246665399 369165616
+1754579039 3936049838 66442917
+4110388406 3616895237 184578890
+158349484 127836567 85004421
+2776115414 4002492755 292474541
+1821021956 3247419973 369475264
+1696382470 3189223404 58196569
+
+light-to-temperature map:
+338228166 2812162941 77503977
+3123877206 693964345 40932068
+3939438903 614787731 633466
+3301169239 2299402886 215156012
+3516325251 499164007 115623724
+3852145506 3365439095 87293397
+875755064 3565078024 729889272
+2849390436 734896413 11914872
+2861305308 215265512 77518872
+4220385528 2056242491 68417151
+2221674563 3167682469 34693717
+2765973467 292784384 83416969
+3198884011 1699097031 22283517
+3164809274 2889666918 34074737
+809366712 746811285 52314986
+4096970661 1633036395 58945085
+3221167528 2699611924 80001711
+697021180 3452732492 112345532
+2059345064 799126271 162329499
+4155915746 629494563 64469782
+2431111524 1721380548 334861943
+684283267 2779613635 12737913
+440342453 2923741655 243940814
+3634265609 961455770 217879897
+4288802679 3202376186 6164617
+415732143 1691981480 4798917
+1605644336 1179335667 453700728
+420531060 2792351548 19811393
+3631948975 1696780397 2316634
+2938824180 2514558898 185053026
+215265512 376201353 122962654
+2256368280 2124659642 174743244
+3940072369 3208540803 156898292
+861681698 615421197 14073366
+
+temperature-to-humidity map:
+841576398 2731200418 60836938
+1860695540 395011682 292982985
+1518037021 3432774193 53954373
+1786573987 2461900019 55353430
+2940303448 1995108352 6974538
+3014069287 1664464874 53916789
+753139746 2190061656 88436652
+2351822957 2925825589 209990361
+3079884326 3498626816 37609115
+4067060121 4186346579 108620717
+4175680838 4102322798 3778367
+1571991394 2415899186 46000833
+2841627583 1157034722 22534242
+1841927417 2517253449 18768123
+2153678525 47765849 108568164
+3251281674 1179568964 226737882
+3067986076 3486728566 11898250
+1308101633 1785172964 209935388
+2262246689 1406306846 89576268
+902413336 2278498308 137400878
+1039814214 3765380846 268287419
+45422022 156334013 238677669
+3617672799 2612163195 119037223
+2947277986 1718381663 66791301
+1617992227 1495883114 168581760
+284099691 687994667 469040055
+4214721882 4106101165 80245414
+2839283756 45422022 2343827
+3117493441 2792037356 133788233
+2864161825 2536021572 76141623
+4179459205 4067060121 35262677
+3736710022 3135815950 296958243
+3478019556 2002082890 139653243
+2610138841 3536235931 229144915
+2561813318 2141736133 48325523
+
+humidity-to-location map:
+608325534 0 231346900
+222429954 453776854 385895580
+3710263359 3540956206 563631409
+1193511298 1116937854 38719102
+1702450793 1176729484 153572024
+1694669826 1109156887 7780967
+0 231346900 222429954
+1856022817 1686715664 1854240542
+1588644556 4104587615 106025270
+1109156887 4210612885 84354411
+4273894768 1155656956 21072528
+1232230400 1330301508 356414156

src/main.rs

@@ -1,76 +1,242 @@
-use std::io::stdin;
+use std::cmp::{max, min};
+use std::{collections::HashMap, io::stdin};
 
-use anyhow::{bail, Result};
+use anyhow::Result;
 use regex::Regex;
 
-/// solve ax² + bx + c = 0
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-fn solve_quadratic(a: f64, b: f64, c: f64) -> (f64, f64) {
+struct Range {
-    let r1 = (-b + f64::sqrt(b * b - 4.0 * a * c)) / 2.0 * a;
+    start: i64,
-    let r2 = (-b - f64::sqrt(b * b - 4.0 * a * c)) / 2.0 * a;
+    len: i64,
-    (r1, r2)
 }
 
-fn parse_input() -> Result<(Vec<i64>, Vec<i64>)> {
+impl Range {
+    fn intersection(&self, other: &Range) -> Option<Range> {
+        let i1 = max(self.start, other.start);
+        let i2 = min(self.start + self.len, other.start + other.len);
+
+        if i1 >= i2 {
+            return None;
+        }
+
+        Some(Range {
+            start: i1,
+            len: i2 - i1,
+        })
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+struct RangeMap {
+    from: i64,
+    to: i64,
+    len: i64,
+}
+
+#[derive(Debug)]
+struct SeedsMap {
+    range_maps: Vec<RangeMap>,
+}
+
+impl SeedsMap {
+    fn new() -> SeedsMap {
+        SeedsMap { range_maps: vec![] }
+    }
+
+    fn add_range(&mut self, range: (i64, i64, i64)) {
+        self.range_maps.push(RangeMap {
+            from: range.1,
+            to: range.0,
+            len: range.2,
+        });
+        self.range_maps.sort_by_key(|r| r.from);
+    }
+
+    fn map(&self, ranges: &[Range]) -> Vec<Range> {
+        let mut result = vec![];
+        for r in ranges {
+            result.extend(self.map_single_range(r));
+        }
+        result
+    }
+
+    fn map_single_range(&self, range: &Range) -> Vec<Range> {
+        if self.range_maps.is_empty() {
+            return vec![*range];
+        }
+
+        let mut result = vec![];
+        let first = self.range_maps.first().unwrap();
+        let last = self.range_maps.last().unwrap();
+        let left = min(range.start, first.from);
+        let right = max(range.start + range.len, last.from + last.len);
+
+        let mut last = left;
+        for rm in &self.range_maps {
+            // first, a range from last to rm.start, with no mapping
+            let r = Range {
+                start: last,
+                len: rm.from - last,
+            };
+            if let Some(i) = r.intersection(range) {
+                result.push(i);
+            }
+            // second, a range from rm.start, with mapping
+            let r = Range {
+                start: rm.from,
+                len: rm.len,
+            };
+            if let Some(i) = r.intersection(range) {
+                result.push(Range {
+                    start: rm.to + i.start - rm.from,
+                    len: i.len,
+                });
+                last = i.start + i.len;
+            }
+        }
+
+        let r = Range {
+            start: last,
+            len: right - last,
+        };
+        if let Some(i) = r.intersection(range) {
+            result.push(i);
+        }
+
+        result
+    }
+}
+
+fn parse_input(seed_ranges: &mut Vec<Range>, maps: &mut HashMap<String, SeedsMap>) -> Result<()> {
     let numbers = Regex::new(r"(\d+)")?;
-    let mut times = vec![];
+    let pairs = Regex::new(r"(\d+) (\d+)")?;
-    let mut distances = vec![];
+    let mut current_map = String::new();
     for line in stdin().lines().map_while(Result::ok) {
-        if line.starts_with("Time:") {
+        if line.starts_with("seeds:") {
-            times = numbers
+            *seed_ranges = pairs
-                .captures_iter(&line.replace(' ', ""))
+                .captures_iter(&line)
-                .map(|c| c.get(1).unwrap().as_str().parse())
+                .map(|c| -> Result<Range> {
-                .map_while(Result::ok)
+                    Ok(Range {
-                .collect();
+                        start: c.get(1).unwrap().as_str().parse()?,
-        } else if line.starts_with("Distance:") {
+                        len: c.get(2).unwrap().as_str().parse()?,
-            distances = numbers
+                    })
-                .captures_iter(&line.replace(' ', ""))
+                })
-                .map(|c| c.get(1).unwrap().as_str().parse())
                 .map_while(Result::ok)
                 .collect();
+        } else if line.ends_with(" map:") {
+            current_map = line
+                .split_whitespace()
+                .next()
+                .unwrap_or_default()
+                .to_owned();
         } else {
-            bail!("unexpected line: {}", line);
+            let nums: Vec<i64> = numbers
+                .captures_iter(&line)
+                .map(|c| c.get(1).unwrap().as_str().parse())
+                .map_while(Result::ok)
+                .collect();
+            if nums.len() == 3 {
+                let map = maps
+                    .entry(current_map.clone())
+                    .or_insert_with(SeedsMap::new);
+                map.add_range((nums[0], nums[1], nums[2]));
+            }
         }
     }
-    Ok((times, distances))
+    Ok(())
 }
 
 fn main() -> Result<()> {
-    let (times, distances) = parse_input()?;
+    let mut maps: HashMap<String, SeedsMap> = HashMap::new();
+    let mut seed_ranges: Vec<Range> = vec![];
 
-    if times.len() != distances.len() {
+    parse_input(&mut seed_ranges, &mut maps)?;
-        bail!(
+
-            "times has {} elements, but distances has {} elements",
+    let map_names = [
-            times.len(),
+        "seed-to-soil",
-            distances.len()
+        "soil-to-fertilizer",
-        );
+        "fertilizer-to-water",
+        "water-to-light",
+        "light-to-temperature",
+        "temperature-to-humidity",
+        "humidity-to-location",
+    ];
+
+    let mut locations = vec![];
+    for range in seed_ranges {
+        let mut mapped_ranges = vec![range];
+        for map_name in map_names {
+            let mapped = maps.get(map_name).unwrap().map(&mapped_ranges);
+            mapped_ranges = mapped;
+        }
+        locations.extend(mapped_ranges.iter().map(|r| r.start));
     }
-
+    println!("{}", locations.iter().min().unwrap());
-    let mut prod = 1;
-    for i in 0..times.len() {
-        let t = times[i];
-        let d = distances[i];
-
-        // the equation to solve is x * (t - x) - d = 0
-        //  = t*x - x*x - d = 0
-        //  = -1x² + tx - d = 0
-        let (r1, r2) = solve_quadratic(-1.0, t as f64, -d as f64);
-        let r1 = (r1 + 1.0).floor() as i64;
-        let r2 = (r2 - 1.0).ceil() as i64;
-
-        let ways = (r2 - r1) + 1;
-
-        println!("{t} {d}");
-        println!("ways: {ways}");
-        prod *= ways;
-    }
-
-    println!("{prod}");
     Ok(())
 }
 
 #[cfg(test)]
 mod tests {
+    use super::*;
 
     #[test]
-    fn test() {}
+    fn test_intersections() {
+        let l = |r1: &Range, r2: &Range| r1.intersection(r2);
+        assert_eq!(
+            l(&Range { start: 1, len: 3 }, &Range { start: 1, len: 3 }),
+            Some(Range { start: 1, len: 3 })
+        );
+        assert_eq!(
+            l(&Range { start: 1, len: 2 }, &Range { start: 1, len: 3 }),
+            Some(Range { start: 1, len: 2 })
+        );
+        assert_eq!(
+            l(&Range { start: 2, len: 4 }, &Range { start: 0, len: 3 }),
+            Some(Range { start: 2, len: 1 })
+        );
+        assert_eq!(
+            l(&Range { start: 0, len: 3 }, &Range { start: 2, len: 4 }),
+            Some(Range { start: 2, len: 1 })
+        );
+        assert_eq!(
+            l(&Range { start: 3, len: 4 }, &Range { start: 0, len: 3 }),
+            None
+        );
+        assert_eq!(
+            l(&Range { start: 0, len: 10 }, &Range { start: 4, len: 4 }),
+            Some(Range { start: 4, len: 4 })
+        );
+    }
+
+    #[test]
+    fn test_range_map() {
+        let mut m = SeedsMap::new();
+        m.add_range((52, 50, 48));
+        m.add_range((50, 98, 2));
+        let r = m.map_single_range(&Range { start: 79, len: 14 });
+        assert_eq!(r, [Range { start: 81, len: 14 }]);
+
+        let mut m = SeedsMap::new();
+        m.add_range((39, 0, 15));
+        m.add_range((0, 15, 37));
+        m.add_range((37, 52, 2));
+        let r = m.map_single_range(&Range { start: 81, len: 14 });
+        assert_eq!(r, [Range { start: 81, len: 14 }]);
+
+        let mut m = SeedsMap::new();
+        m.add_range((88, 18, 7));
+        m.add_range((18, 25, 70));
+        let r = m.map_single_range(&Range { start: 81, len: 14 });
+        assert_eq!(r, [Range { start: 74, len: 14 }]);
+
+        let mut m = SeedsMap::new();
+        m.add_range((81, 45, 19));
+        m.add_range((68, 64, 13));
+        m.add_range((45, 77, 23));
+        let r = m.map_single_range(&Range { start: 74, len: 14 });
+        assert_eq!(
+            r,
+            [Range { start: 78, len: 3 }, Range { start: 45, len: 11 }]
+        );
+    }
 }