AoC, Day 11, Parts 1 and 2 (Solved)
This commit is contained in:
🐙PiperYxzzy
111
2023/11/README.md
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111
2023/11/README.md
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## \-\-\- Day 11: Cosmic Expansion ---
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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.
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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.
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Maybe you can help him with the analysis to speed things up?
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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:
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```
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...#......
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.......#..
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#.........
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..........
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......#...
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.#........
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.........#
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..........
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.......#..
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#...#.....
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```
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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.
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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.
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In the above example, three columns and two rows contain no galaxies:
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```
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v v v
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...#......
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.......#..
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#.........
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>..........<
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......#...
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.#........
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.........#
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>..........<
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.......#..
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#...#.....
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^ ^ ^
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```
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These rows and columns need to be _twice as big_; the result of cosmic expansion therefore looks like this:
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```
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....#........
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.........#...
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#............
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.............
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.............
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........#....
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.#...........
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............#
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.............
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.............
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.........#...
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#....#.......
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```
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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:
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```
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....1........
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.........2...
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3............
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.............
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.............
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........4....
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.5...........
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............6
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.............
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.............
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.........7...
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8....9.......
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```
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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.)
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For example, here is one of the shortest paths between galaxies `5` and `9`:
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```
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....1........
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.........2...
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3............
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.............
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.............
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........4....
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.5...........
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.##.........6
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..##.........
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...##........
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....##...7...
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8....9.......
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```
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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:
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- Between galaxy `1` and galaxy `7`: 15
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- Between galaxy `3` and galaxy `6`: 17
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- Between galaxy `8` and galaxy `9`: 5
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In this example, after expanding the universe, the sum of the shortest path between all 36 pairs of galaxies is `374`.
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Expand the universe, then find the length of the shortest path between every pair of galaxies. _What is the sum of these lengths?_
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114
2023/11/code.go
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114
2023/11/code.go
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package main
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import (
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"math"
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"strings"
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"github.com/jpillora/puzzler/harness/aoc"
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)
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func main() {
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aoc.Harness(run)
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}
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// on code change, run will be executed 4 times:
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// 1. with: false (part1), and example input
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// 2. with: true (part2), and example input
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// 3. with: false (part1), and user input
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// 4. with: true (part2), and user input
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// the return value of each run is printed to stdout
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func run(part2 bool, input string) any {
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universe := make([][]rune, 0)
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for _, l := range strings.Split(input, "\n") {
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if l == "" {
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continue
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}
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line := make([]rune, 0)
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empty := true
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for r := range strings.Split(l, "") {
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if rune(l[r]) != '.' {
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empty = false
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}
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line = append(line, rune(l[r]))
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}
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if empty {
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for e := range line {
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line[e] = '↕'
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}
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}
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universe = append(universe, line)
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}
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// Now expand inner cols
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for h := 0; h < len(universe[0]); h++ {
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empty := true
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for v := range universe {
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if universe[v][h] != '.' && universe[v][h] != '↕' {
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empty = false
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}
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}
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if empty {
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for v := range universe {
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if universe[v][h] == '↕' {
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universe[v][h] = '⥁'
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} else {
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universe[v][h] = '↔'
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}
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}
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}
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}
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// when you're ready to do part 2, remove this "not implemented" block
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factor := 1
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if part2 {
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factor = 1000000
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} else {
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// solve part 1 here
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factor = 2
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}
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coords := make([][]int, 0)
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vr := 0
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for v := range universe {
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if universe[v][0] == '↕' || universe[v][0] == '⥁' {
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// expand else normal v
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vr += factor
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} else {
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vr += 1
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}
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hr := 0
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for h := range universe {
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if universe[0][h] == '↔' || universe[0][h] == '⥁' {
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hr += factor
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} else {
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hr += 1
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}
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if universe[v][h] == '#' {
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coords = append(coords, []int{vr, hr})
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}
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}
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}
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sumHyp := 0
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compared := 0
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for c1 := 0; c1 < len(coords)-1; c1++ {
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for c2 := c1 + 1; c2 < len(coords); c2++ {
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// add rise and run?
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lenv := int(math.Abs(float64(coords[c1][0] - coords[c2][0])))
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lenh := int(math.Abs(float64(coords[c1][1] - coords[c2][1])))
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// convert to int?
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sumHyp += lenv + lenh
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compared++
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}
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}
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return sumHyp
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}
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10
2023/11/input-example.txt
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2023/11/input-example.txt
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...#......
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.......#..
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#.........
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..........
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......#...
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.#........
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.........#
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..........
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.......#..
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#...#.....
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140
2023/11/input-user.txt
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140
2023/11/input-user.txt
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..........#............................................#..........#.....#...........................................#.......#.........#.....
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.....#...................#..............#....................................................#..............................................
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..............................#....................#...................................................#....................................
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.............................................#.....................................................................................#........
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............#................................................................#......#.......................................................
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......................................#..................#.........................................#........................................
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.............................................................................................................................#..............
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.................#.....#....................................................................................................................
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.....................................................#...........#..........................................#.............................#.
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.....#..........................#...............#.......................................#...........................#.......................
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....................#................#...............................#.........................#.....#......................................
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...........#.............................................#..................................................................................
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................................................................................................................................#.....#.....
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................#...................................#...........#......................................................#....................
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.........................#.................................................#.................................#.............................#
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...#..............................#...................................#................................#....................................
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...............................................................................#............................................................
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..................................................................#...........................#..........................#........#.........
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.........#....................#........................................................................................................#....
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..........................................................................#..............#........................#.........................
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....................#...............................#........#..............................................................................
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..#..............................#........#...................................#..........................#..................#...............
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......................................................................#...........................#............#...................#........
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........#................#..............................#.............................................................#.................#...
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......................................#......#....................#........#.....#.........#................................................
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.....................#............................#.............................................................................#...........
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....#.........................#.............................................................................#...............................
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............#..................................................#................................#...........................#...............
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....................................................................................#..................#.............#......................
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..........................................................................................................................................#.
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...................................#...............#.....................................#.......................#..........................
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..#................#.......................#................................................................................................
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...........#...............#...........................................#.................................................#.........#........
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......#.....................................................................#............................#..................................
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.........................................................#..................................................................................
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...................................................................#........................................................................
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.........#....................................................#......................................#............#....................#....
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...................................................#....................#...........#......................#...............#................
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..#..............................#......#........................................................#..........................................
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........................................................#...........................................................................#.......
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......................................................................................................................#.....................
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......#......................................................................#................#.............................................
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............................................#..............#............................................#...................#...............
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.......................#........#......#........................#..................................................#........................
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....................................................#......................................#.......#.........#..............................
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........#..........................................................................................................................#........
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................#...........................................................................................................................
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#..........................#.......#......#.............................#.................................#.................................
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......................................................#.............................#............#.......................#.....#............
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...................#.............................................#...........#...........#..............................................#...
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...............................#..................#..........................................................#..............................
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..............#..............................................#.......................................#......................................
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..#.....................#.............#........................................................#............................................
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...................................................................#........................................................................
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............................................................................................................................................
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........#.......#.....................................................................#.....................................................
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...............................#.....................#..................#.....................................#.........#...................
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..............................................#...............................#............#........#.......................................
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.#.................#........................................................................................................................
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..................................#................................................#.....................................................#..
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............................................................................................................................................
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...........#..................#....................#....................................#...................................................
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....#....................................#.........................#.....#......................#...............#..............#............
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.................................................................................#..........................................................
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...............................................#........................................................#...........#.....................#.
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........................#........#.........................#................................................................................
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....................................................................................#..............................................#........
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...#......................................#.................................................................................................
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.....................................................#.........................................#......#.........#...........................
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..............................#..........................................................#.................#................#...............
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..............#....................................................#......#.................................................................
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........#............#..........................................................................................................#...........
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............................................................................................................................................
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...........................#.....................#..............#..................................#................................#.......
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............................................................................#...............................................................
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.............................................#..........................................................#.................................#.
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.....................................................#..............#.......................................................................
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......#................#................#..................#.................................................#...........#..................
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................#.................#......................................#........................................#...........#.............
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...........#....................................#................#..........................#......................................#........
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............................................................................................................................................
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...................#..................................#.....................................................................................
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...#.......................#..............#.................#..............#..........#...................................................#.
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......................................................................................................#................#.............#......
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....................................................................#............................#..............................#...........
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...............................#..................#.......................................#...............#................#................
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............................................................................................................................................
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............................................................................................................................................
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......................#...............................#..........#.............................................#...................#........
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........................................#..............................................................#.................#..................
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..........................#........#.......................................#..........#....................................................#
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..................#...........................#.............................................................................................
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......#....................................................#...............................#................................................
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..............................#.............................................................................................................
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................................................................................................#........#..................................
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#.............#.......................................................#........#...............................................#.......#....
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...........................#...................................................................................#............................
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....#...................................#...................................................................................................
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................................................#......#..................................................................................#.
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.......................................................................................#.............#......................................
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................................#..........................#..................#...........................#.................................
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....................#...........................................................................................#...................#.......
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...................................................#..............#.......#............................................#....................
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..#.........................................................................................................................................
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........#.....#.......................#.......#..............................................................................#..............
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......................#.......#.........................#........................#...........#.......#...................................#..
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...............................................................................................................#............................
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.......................................................................................#..................#.................................
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........................................................................#.........................#..................#......................
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Reference in New Issue
Block a user