40 lines
1.3 KiB
Text
40 lines
1.3 KiB
Text
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#!/usr/bin/env kotlin
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import java.io.File
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operator fun <E> List<List<E>>.get(position: Pair<Int, Int>): E = this[position.first][position.second]
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val trailheads = mutableListOf<Pair<Int, Int>>()
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val grid = File("input.txt").readLines().mapIndexed { row, line ->
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line.toCharArray().mapIndexed { col, char ->
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if (char == '0') trailheads.add(row to col)
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char.digitToInt()
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}
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}
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var sum = 0
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for (trailhead in trailheads) {
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val positions = mutableListOf(trailhead)
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while (!positions.all { pos -> grid[pos] == 9 }) {
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val iter = positions.listIterator()
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while (iter.hasNext()) {
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val pos = iter.next()
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iter.remove()
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if (grid[pos] == 9) {
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break
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}
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if (grid[pos.first].getOrNull(pos.second - 1) == grid[pos] + 1) iter.add(pos.first to pos.second - 1)
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if (grid[pos.first].getOrNull(pos.second + 1) == grid[pos] + 1) iter.add(pos.first to pos.second + 1)
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if (grid.getOrNull(pos.first + 1)?.get(pos.second) == grid[pos] + 1) iter.add(pos.first + 1 to pos.second)
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if (grid.getOrNull(pos.first - 1)?.get(pos.second) == grid[pos] + 1) iter.add(pos.first - 1 to pos.second)
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}
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}
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val tops = positions.toHashSet().size
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sum += tops
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}
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println("Result: $sum")
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