109 lines
1.9 KiB
D
109 lines
1.9 KiB
D
import std;
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void main()
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{
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File("input", "r").byLineCopy.array.productOfTreesForDefaultSlopes.writeln;
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}
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alias product = partial!(reverseArgs!(fold!((a, b) => a * b)), 1UL);
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auto productOfTreesForDefaultSlopes(const char[][] input)
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{
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return [tuple(1, 1), tuple(3, 1), tuple(5, 1), tuple(7, 1), tuple(1, 2)].map!(
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slope => input.dup.countTrees(slope[0], slope[1])).product;
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}
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auto countTrees(const char[][] input, int angleX, int angleY)
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in(input.length > 0)
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{
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immutable width = input[0].length;
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return input.stride(angleY).enumerate
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.map!(row => row.value[(row.index * angleX) % width])
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.filter!(pos => pos == '#')
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.count;
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}
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unittest
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{
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auto input = `..##.......
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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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.#..#...#.#`.byChar.splitter("\n").map!array.array;
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assert(input.countTrees(1, 1) == 2);
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}
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unittest
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{
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auto input = `..##.......
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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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.#..#...#.#`.byChar.splitter("\n").map!array.array;
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assert(input.countTrees(3, 1) == 7);
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}
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unittest
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{
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auto input = `..##.......
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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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.#..#...#.#`.byChar.splitter("\n").map!array.array;
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assert(input.countTrees(5, 1) == 3);
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}
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unittest
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{
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auto input = `..##.......
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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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.#..#...#.#`.byChar.splitter("\n").map!array.array;
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assert(input.countTrees(7, 1) == 4);
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}
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unittest
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{
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auto input = `..##.......
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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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.#..#...#.#`.byChar.splitter("\n").map!array.array;
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assert(input.countTrees(1, 2) == 2);
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}
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