AoC, Day 11, Parts 1 and 2 (Solved)

2023/11/README.md

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+## \-\-\- Day 11: Cosmic Expansion ---
+
+You continue following signs for "Hot Springs" and eventually come across an [observatory](https://en.wikipedia.org/wiki/Observatory). The Elf within turns out to be a researcher studying cosmic expansion using the giant telescope here.
+
+He doesn't know anything about the missing machine parts; he's only visiting for this research project. However, he confirms that the hot springs are the next-closest area likely to have people; he'll even take you straight there once he's done with today's observation analysis.
+
+Maybe you can help him with the analysis to speed things up?
+
+The researcher has collected a bunch of data and compiled the data into a single giant _image_ (your puzzle input). The image includes _empty space_ ( `.`) and _galaxies_ ( `#`). For example:
+
+```
+...#......
+.......#..
+#.........
+..........
+......#...
+.#........
+.........#
+..........
+.......#..
+#...#.....
+
+```
+
+The researcher is trying to figure out the sum of the lengths of the _shortest path between every pair of galaxies_. However, there's a catch: the universe expanded in the time it took the light from those galaxies to reach the observatory.
+
+Due to something involving gravitational effects, _only some space expands_. In fact, the result is that _any rows or columns that contain no galaxies_ should all actually be twice as big.
+
+In the above example, three columns and two rows contain no galaxies:
+
+```
+   v  v  v
+ ...#......
+ .......#..
+ #.........
+>..........<
+ ......#...
+ .#........
+ .........#
+>..........<
+ .......#..
+ #...#.....
+   ^  ^  ^
+
+```
+
+These rows and columns need to be _twice as big_; the result of cosmic expansion therefore looks like this:
+
+```
+....#........
+.........#...
+#............
+.............
+.............
+........#....
+.#...........
+............#
+.............
+.............
+.........#...
+#....#.......
+
+```
+
+Equipped with this expanded universe, the shortest path between every pair of galaxies can be found. It can help to assign every galaxy a unique number:
+
+```
+....1........
+.........2...
+3............
+.............
+.............
+........4....
+.5...........
+............6
+.............
+.............
+.........7...
+8....9.......
+
+```
+
+In these 9 galaxies, there are _36 pairs_. Only count each pair once; order within the pair doesn't matter. For each pair, find any shortest path between the two galaxies using only steps that move up, down, left, or right exactly one `.` or `#` at a time. (The shortest path between two galaxies is allowed to pass through another galaxy.)
+
+For example, here is one of the shortest paths between galaxies `5` and `9`:
+
+```
+....1........
+.........2...
+3............
+.............
+.............
+........4....
+.5...........
+.##.........6
+..##.........
+...##........
+....##...7...
+8....9.......
+
+```
+
+This path has length `9` because it takes a minimum of _nine steps_ to get from galaxy `5` to galaxy `9` (the eight locations marked `#` plus the step onto galaxy `9` itself). Here are some other example shortest path lengths:
+
+- Between galaxy `1` and galaxy `7`: 15
+- Between galaxy `3` and galaxy `6`: 17
+- Between galaxy `8` and galaxy `9`: 5
+
+In this example, after expanding the universe, the sum of the shortest path between all 36 pairs of galaxies is `374`.
+
+Expand the universe, then find the length of the shortest path between every pair of galaxies. _What is the sum of these lengths?_

2023/11/code.go

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+package main
+
+import (
+	"math"
+	"strings"
+
+	"github.com/jpillora/puzzler/harness/aoc"
+)
+
+func main() {
+	aoc.Harness(run)
+}
+
+// on code change, run will be executed 4 times:
+// 1. with: false (part1), and example input
+// 2. with: true (part2), and example input
+// 3. with: false (part1), and user input
+// 4. with: true (part2), and user input
+// the return value of each run is printed to stdout
+func run(part2 bool, input string) any {
+
+	universe := make([][]rune, 0)
+	for _, l := range strings.Split(input, "\n") {
+		if l == "" {
+			continue
+		}
+		line := make([]rune, 0)
+		empty := true
+		for r := range strings.Split(l, "") {
+			if rune(l[r]) != '.' {
+				empty = false
+			}
+			line = append(line, rune(l[r]))
+		}
+
+		if empty {
+			for e := range line {
+				line[e] = '↕'
+			}
+		}
+		universe = append(universe, line)
+	}
+
+	// Now expand inner cols
+	for h := 0; h < len(universe[0]); h++ {
+		empty := true
+		for v := range universe {
+			if universe[v][h] != '.' && universe[v][h] != '↕' {
+				empty = false
+			}
+		}
+
+		if empty {
+			for v := range universe {
+				if universe[v][h] == '↕' {
+					universe[v][h] = '⥁'
+				} else {
+					universe[v][h] = '↔'
+				}
+			}
+		}
+	}
+
+	// when you're ready to do part 2, remove this "not implemented" block
+	factor := 1
+	if part2 {
+		factor = 1000000
+	} else {
+		// solve part 1 here
+		factor = 2
+	}
+
+	coords := make([][]int, 0)
+
+	vr := 0
+	for v := range universe {
+		if universe[v][0] == '↕' || universe[v][0] == '⥁' {
+			// expand else normal v
+			vr += factor
+		} else {
+			vr += 1
+		}
+
+		hr := 0
+		for h := range universe {
+			if universe[0][h] == '↔' || universe[0][h] == '⥁' {
+				hr += factor
+			} else {
+				hr += 1
+			}
+
+			if universe[v][h] == '#' {
+				coords = append(coords, []int{vr, hr})
+			}
+		}
+	}
+
+	sumHyp := 0
+	compared := 0
+	for c1 := 0; c1 < len(coords)-1; c1++ {
+		for c2 := c1 + 1; c2 < len(coords); c2++ {
+			// add rise and run?
+			lenv := int(math.Abs(float64(coords[c1][0] - coords[c2][0])))
+			lenh := int(math.Abs(float64(coords[c1][1] - coords[c2][1])))
+
+			// convert to int?
+			sumHyp += lenv + lenh
+
+			compared++
+		}
+	}
+
+	return sumHyp
+}

2023/11/input-example.txt

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+...#......
+.......#..
+#.........
+..........
+......#...
+.#........
+.........#
+..........
+.......#..
+#...#.....

2023/11/input-user.txt

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+..........#............................................#..........#.....#...........................................#.......#.........#.....
+.....#...................#..............#....................................................#..............................................
+..............................#....................#...................................................#....................................
+.............................................#.....................................................................................#........
+............#................................................................#......#.......................................................
+......................................#..................#.........................................#........................................
+.............................................................................................................................#..............
+.................#.....#....................................................................................................................
+.....................................................#...........#..........................................#.............................#.
+.....#..........................#...............#.......................................#...........................#.......................
+....................#................#...............................#.........................#.....#......................................
+...........#.............................................#..................................................................................
+................................................................................................................................#.....#.....
+................#...................................#...........#......................................................#....................
+.........................#.................................................#.................................#.............................#
+...#..............................#...................................#................................#....................................
+...............................................................................#............................................................
+..................................................................#...........................#..........................#........#.........
+.........#....................#........................................................................................................#....
+..........................................................................#..............#........................#.........................
+....................#...............................#........#..............................................................................
+..#..............................#........#...................................#..........................#..................#...............
+......................................................................#...........................#............#...................#........
+........#................#..............................#.............................................................#.................#...
+......................................#......#....................#........#.....#.........#................................................
+.....................#............................#.............................................................................#...........
+....#.........................#.............................................................................#...............................
+............#..................................................#................................#...........................#...............
+....................................................................................#..................#.............#......................
+..........................................................................................................................................#.
+...................................#...............#.....................................#.......................#..........................
+..#................#.......................#................................................................................................
+...........#...............#...........................................#.................................................#.........#........
+......#.....................................................................#............................#..................................
+.........................................................#..................................................................................
+...................................................................#........................................................................
+.........#....................................................#......................................#............#....................#....
+...................................................#....................#...........#......................#...............#................
+..#..............................#......#........................................................#..........................................
+........................................................#...........................................................................#.......
+......................................................................................................................#.....................
+......#......................................................................#................#.............................................
+............................................#..............#............................................#...................#...............
+.......................#........#......#........................#..................................................#........................
+....................................................#......................................#.......#.........#..............................
+........#..........................................................................................................................#........
+................#...........................................................................................................................
+#..........................#.......#......#.............................#.................................#.................................
+......................................................#.............................#............#.......................#.....#............
+...................#.............................................#...........#...........#..............................................#...
+...............................#..................#..........................................................#..............................
+..............#..............................................#.......................................#......................................
+..#.....................#.............#........................................................#............................................
+...................................................................#........................................................................
+............................................................................................................................................
+........#.......#.....................................................................#.....................................................
+...............................#.....................#..................#.....................................#.........#...................
+..............................................#...............................#............#........#.......................................
+.#.................#........................................................................................................................
+..................................#................................................#.....................................................#..
+............................................................................................................................................
+...........#..................#....................#....................................#...................................................
+....#....................................#.........................#.....#......................#...............#..............#............
+.................................................................................#..........................................................
+...............................................#........................................................#...........#.....................#.
+........................#........#.........................#................................................................................
+....................................................................................#..............................................#........
+...#......................................#.................................................................................................
+.....................................................#.........................................#......#.........#...........................
+..............................#..........................................................#.................#................#...............
+..............#....................................................#......#.................................................................
+........#............#..........................................................................................................#...........
+............................................................................................................................................
+...........................#.....................#..............#..................................#................................#.......
+............................................................................#...............................................................
+.............................................#..........................................................#.................................#.
+.....................................................#..............#.......................................................................
+......#................#................#..................#.................................................#...........#..................
+................#.................#......................................#........................................#...........#.............
+...........#....................................#................#..........................#......................................#........
+............................................................................................................................................
+...................#..................................#.....................................................................................
+...#.......................#..............#.................#..............#..........#...................................................#.
+......................................................................................................#................#.............#......
+....................................................................#............................#..............................#...........
+...............................#..................#.......................................#...............#................#................
+............................................................................................................................................
+............................................................................................................................................
+......................#...............................#..........#.............................................#...................#........
+........................................#..............................................................#.................#..................
+..........................#........#.......................................#..........#....................................................#
+..................#...........................#.............................................................................................
+......#....................................................#...............................#................................................
+..............................#.............................................................................................................
+................................................................................................#........#..................................
+#.............#.......................................................#........#...............................................#.......#....
+...........................#...................................................................................#............................
+....#...................................#...................................................................................................
+................................................#......#..................................................................................#.
+.......................................................................................#.............#......................................
+................................#..........................#..................#...........................#.................................
+....................#...........................................................................................#...................#.......
+...................................................#..............#.......#............................................#....................
+..#.........................................................................................................................................
+........#.....#.......................#.......#..............................................................................#..............
+......................#.......#.........................#........................#...........#.......#...................................#..
+...............................................................................................................#............................
+.......................................................................................#..................#.................................
+........................................................................#.........................#..................#......................
+..........................................#.....#.........................................................................#.................
+..................#..........#...............................#..............................................................................
+......................................#........................................#.........#..................................................
+...#...............................................................................................................#....................#...
+........#..............................................#...............#.....................................................#..............
+...................................#........................................#...............#............#..........................#.......
+............#.................#.............................................................................................................
+....................#.............................#.........................................................................................
+....................................................................................#..............#........................................
+...............#......................................#.......................................#.........................................#...
+.#........................#........................................#...............................................#......#.................
+........................................#.................................................#.................................................
+.....#...................................................................#..................................................................
+..................................................................................................#............#............................
+............#.......#.........#.....#...............#.......#...........................................#...................................
+..#..........................................#......................#..................#...............................................#....
+............................................................................................................................................
+.........................#.............#....................................................................................................
+..................................................#............................#................................#...................#.......
+...................................#..............................................................#......#..................................
+............................................................................................................................................
+........................................................#.....#............................#..........................#.....#...............
+......................#.......................#..........................#.............................................................#....
+......#.....#.........................................................................................#.....................................
+..................................................................#...............................................................#.........
+...................................#.........................................#.................#..........................#...............#.
+..#.........................................#.........................#..............#......................................................
+...................................................#......................................#...................#.............................
+.........................................................#..................................................................................
+..............#................................................#..................................#.........................................
+...................#..........#..........#................................................................#......#............#............#