84 lines
2.0 KiB
Nim
84 lines
2.0 KiB
Nim
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import sequtils
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import future
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import nre except toSeq
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type
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Direction = enum
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up = 0, left = 1, down = 2, right = 3
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Grid = seq[seq[char]]
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const directions = [up, left, down, right]
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proc indexOf(hay: seq[char], needle: char): int =
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# It almost seems weird that this doesn’t already exist...
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# It probably does, and I just missed it. Whatever, no error handling because :lul:
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var i = 0
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while hay[i] != needle:
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i += 1
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return i
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proc gridGet(g: Grid, p: array[2, int]): char =
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return g[p[0]][p[1]]
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proc changePosition(current: array[2, int], dir: Direction): array[2, int] =
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if dir == up:
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return [current[0]-1, current[1]]
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if dir == left:
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return [current[0], current[1]-1]
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if dir == down:
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return [current[0]+1, current[1]]
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if dir == right:
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return [current[0], current[1]+1]
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proc oppositeDirection(d: Direction): Direction =
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# the better solution would be something like
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# mod(getEnumOrdinal(direction, $direction) + 2, 4)
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# but that doesn’t quite work because I’m bad at this whole thing
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case d
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of up: return down
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of left: return right
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of down: return up
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of right: return left
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else: discard
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proc changeDirection(g: Grid, pos: array[2, int], direction: Direction): Direction =
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for d in directions:
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if d != oppositeDirection(direction) and gridGet(g, changePosition(pos, d)) != ' ':
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return d
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let grid = lc[toSeq(line.items()) | (line <- lines("input.txt")), seq[char]]
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var position = [0, indexOf(grid[0], '|')]
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var direction = down
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var done = false
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var visited = ""
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var newchar: char
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var steps = 1
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while not done:
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#echo position[0], ", ", position[1]
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#echo direction
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var newpos = changePosition(position, direction)
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newchar = gridGet(grid, newpos)
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#echo(newchar)
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if newchar in ['|', '-']:
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inc steps
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elif newchar == '+':
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inc steps
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direction = changeDirection(grid, newpos, direction)
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elif nre.contains($newchar, re"[A-Z]"):
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inc steps
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visited &= newchar
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elif newchar == ' ':
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done = true
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position = newpos
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echo(visited)
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echo(steps)
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