2019: day03: part 1

aoc2019/input/day03.txt

@@ -0,0 +1,2 @@
+R1009,U993,L383,D725,R163,D312,R339,U650,R558,U384,R329,D61,L172,D555,R160,D972,L550,D801,L965,U818,L123,D530,R176,D353,L25,U694,L339,U600,L681,D37,R149,D742,R762,U869,R826,U300,L949,U978,L303,U361,R136,D343,L909,U551,R745,U913,L566,D292,R820,U886,R205,D431,L93,D71,R577,U872,L705,U510,L698,U963,R607,U527,L669,D543,R690,U954,L929,D218,R490,U500,L589,D332,R949,D538,R696,U659,L188,U468,L939,U833,L445,D430,R78,D303,R130,D649,R849,D712,L511,U745,R51,U973,R799,U829,R605,D771,L837,U204,L414,D427,R538,U116,R540,D168,R493,U900,L679,U431,L521,D500,L428,U332,L954,U717,L853,D339,L88,U807,L607,D496,L163,U468,L25,U267,L759,D898,L591,U445,L469,U531,R596,D486,L728,D677,R350,D429,R39,U568,R92,D875,L835,D841,R877,U178,L221,U88,R592,U692,R455,U693,L419,U90,R609,U672,L293,U168,R175,D456,R319,D570,R504,D165,L232,D624,L604,D68,R807,D59,R320,D281,L371,U956,L788,D897,L231,D829,R287,D798,L443,U194,R513,D925,L232,U225,L919,U563,R448,D889,R661,U852,L950,D558,L269,U186,L625,U673,L995,U732,R435,U849,L413,D690,L158,D234,R361,D458,L271,U90,L781,U754,R256,U162,L842,U927,L144,D62,R928,D238,R473,U97,L745,U303,L487,D349,L520,D31,L825,U385,L133,D948,L39,U62,R801,D664,L333,U134,R692,U385,L658,U202,L279,D374,R489,D686,L182,U222,R733,U177,R94,D603,L376,U901,R216,D851,L155,D214,L460,U758,R121,D746,L180,U175,L943,U146,L166,D251,L238,U168,L642,D341,R281,U182,R539,D416,R553,D67,L748,U272,R257,D869,L340,U180,R791,U138,L755,D976,R731,U713,R602,D284,L258,U176,R509,U46,R935,U576,R96,U89,L913,U703,R833
+L1006,D998,R94,D841,R911,D381,R532,U836,L299,U237,R781,D597,L399,D800,L775,D405,L485,U636,R589,D942,L878,D779,L751,U711,L973,U410,L151,U15,L685,U417,L106,D648,L105,D461,R448,D743,L589,D430,R883,U37,R155,U350,L421,U23,R337,U816,R384,D671,R615,D410,L910,U914,L579,U385,R916,U13,R268,D519,R289,U410,L389,D885,L894,U734,L474,U707,L72,U155,L237,U760,L127,U806,L15,U381,L557,D727,L569,U320,L985,D452,L8,D884,R356,U732,L672,D458,L485,U402,L238,D30,R644,U125,R753,U183,L773,U487,R849,U210,L164,D808,L595,D668,L340,U785,R313,D72,L76,D263,R689,U604,R471,U688,R462,D915,R106,D335,R869,U499,R190,D916,R468,D882,R56,D858,L143,D741,L386,U856,R50,U853,R151,D114,L773,U854,L290,D344,L23,U796,L531,D932,R314,U960,R643,D303,L661,D493,L82,D491,L722,U848,L686,U4,L985,D509,L135,D452,R500,U105,L326,D101,R222,D944,L645,D362,L628,U305,L965,U356,L358,D137,R787,U728,R967,U404,R18,D928,L695,D965,R281,D597,L791,U731,R746,U163,L780,U41,L255,U81,L530,D964,R921,D297,R475,U663,L226,U623,L984,U943,L143,U201,R926,U572,R343,U839,R764,U751,R128,U939,R987,D108,R474,U599,R412,D248,R125,U797,L91,D761,L840,U290,L281,U779,R650,D797,R185,D320,L25,U378,L696,U332,R75,D620,L213,D667,R558,U267,L846,U306,R939,D220,R311,U827,R345,U534,R56,D679,R48,D845,R898,U8,R862,D960,R753,U319,L886,D795,R805,D265,R876,U729,R894,D368,R858,U744,R506,D327,L903,U919,L721,U507,L463,U753,R775,D719,R315,U128,R17,D376,R999,D386,L259,U181,L162,U605,L265,D430,R35,D968,R207,U466,R796,D667,R93,U749,L315,D410,R312,U929,L923,U260,R638

aoc2019/src/day03.rs

@@ -0,0 +1,159 @@
+use std::collections::HashSet;
+use std::error::Error;
+use std::str::FromStr;
+
+use aoc::err;
+use aoc::Result;
+
+const INPUT: &str = include_str!("../input/day03.txt");
+
+pub fn run() -> Result<()> {
+    println!("part 1: {}", part1(INPUT)?);
+    Ok(())
+}
+
+enum Move {
+    Up(i64),
+    Down(i64),
+    Left(i64),
+    Right(i64),
+}
+
+impl FromStr for Move {
+    type Err = Box<dyn Error>;
+
+    fn from_str(s: &str) -> Result<Self> {
+        let direction = s
+            .chars()
+            .nth(0)
+            .ok_or_else(|| err!("couldn't get direction char in move: {}", s))?;
+
+        let s = s
+            .get(1..)
+            .ok_or_else(|| err!("move missing length: {}", s))?;
+
+        let length = s.parse()?;
+
+        match direction {
+            'U' => Ok(Move::Up(length)),
+            'D' => Ok(Move::Down(length)),
+            'L' => Ok(Move::Left(length)),
+            'R' => Ok(Move::Right(length)),
+            _ => Err(err!("couldn't parse direction: {}", direction)),
+        }
+    }
+}
+
+fn parse_path(line: &str) -> Result<Vec<Move>> {
+    line.trim_end().split(',').map(|m| m.parse()).collect()
+}
+
+fn path(mut a: (i64, i64), b: (i64, i64)) -> Vec<(i64, i64)> {
+    let mut res = Vec::new();
+
+    while a != b {
+        if a.0 < b.0 {
+            a.0 += 1;
+        } else if a.0 > b.0 {
+            a.0 -= 1;
+        }
+
+        if a.1 < b.1 {
+            a.1 += 1;
+        } else if a.1 > b.1 {
+            a.1 -= 1;
+        }
+
+        res.push(a);
+    }
+
+    res
+}
+
+fn manhattan_distance(a: (i64, i64), b: (i64, i64)) -> i64 {
+    (a.0 - b.0).abs() + (a.1 - b.1).abs()
+}
+
+fn part1(input: &str) -> Result<i64> {
+    let mut lines = input.lines();
+    let first_path = parse_path(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
+    let second_path = parse_path(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
+
+    let mut first_x = 0;
+    let mut first_y = 0;
+
+    let mut second_x = 0;
+    let mut second_y = 0;
+
+    let mut first_locations = HashSet::new();
+    let mut cross_locations = HashSet::new();
+
+    for mv in first_path {
+        let new_pos = match mv {
+            Move::Up(dy) => (first_x, first_y - dy),
+            Move::Down(dy) => (first_x, first_y + dy),
+            Move::Left(dx) => (first_x - dx, first_y),
+            Move::Right(dx) => (first_x + dx, first_y),
+        };
+
+        for cell in path((first_x, first_y), new_pos) {
+            first_locations.insert(cell);
+        }
+
+        first_x = new_pos.0;
+        first_y = new_pos.1;
+    }
+
+    for mv in second_path {
+        let new_pos = match mv {
+            Move::Up(dy) => (second_x, second_y - dy),
+            Move::Down(dy) => (second_x, second_y + dy),
+            Move::Left(dx) => (second_x - dx, second_y),
+            Move::Right(dx) => (second_x + dx, second_y),
+        };
+
+        for cell in path((second_x, second_y), new_pos) {
+            if first_locations.contains(&cell) {
+                cross_locations.insert(cell);
+            }
+        }
+
+        second_x = new_pos.0;
+        second_y = new_pos.1;
+    }
+
+    cross_locations
+        .iter()
+        .map(|(x, y)| manhattan_distance((*x, *y), (0, 0)))
+        .min()
+        .ok_or_else(|| err!("the cables never crossed !"))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const PROVIDED1: &str = "R8,U5,L5,D3
+U7,R6,D4,L4
+";
+
+    const PROVIDED2: &str = "R75,D30,R83,U83,L12,D49,R71,U7,L72
+U62,R66,U55,R34,D71,R55,D58,R83
+";
+
+    const PROVIDED3: &str = "R98,U47,R26,D63,R33,U87,L62,D20,R33,U53,R51
+U98,R91,D20,R16,D67,R40,U7,R15,U6,R7
+";
+
+    #[test]
+    fn part1_provided() {
+        assert_eq!(part1(PROVIDED1).unwrap(), 6);
+        assert_eq!(part1(PROVIDED2).unwrap(), 159);
+        assert_eq!(part1(PROVIDED3).unwrap(), 135);
+    }
+
+    #[test]
+    fn part1_real() {
+        assert_eq!(part1(INPUT).unwrap(), 273);
+    }
+}

aoc2019/src/lib.rs

@@ -1,2 +1,3 @@
 pub mod day01;
 pub mod day02;
+pub mod day03;

aoc2019/src/main.rs

@@ -2,9 +2,10 @@ use aoc::Result;
 
 use aoc2019::day01;
 use aoc2019::day02;
+use aoc2019::day03;
 
 fn main() -> Result<()> {
-    let days: &[fn() -> Result<()>] = &[day01::run, day02::run];
+    let days: &[fn() -> Result<()>] = &[day01::run, day02::run, day03::run];
 
     aoc::run(days)
 }