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139 lines
3.6 KiB
139 lines
3.6 KiB
#!/usr/bin/env julia
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using Test
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struct Move
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direction :: Char
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count :: Int
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end
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mutable struct KnotPair
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head_x :: Int
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head_y :: Int
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tail_x :: Int
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tail_y :: Int
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end
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function parse_move(line)
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parts = split(line, limit=2)
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return Move(parts[1][1], parse(Int, parts[2]))
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end
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function state_changed(old_state, new_state)
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return (new_state.head_x != old_state.head_x
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|| new_state.head_y != old_state.head_y
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|| new_state.tail_x != old_state.tail_x
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|| new_state.tail_y != old_state.tail_y)
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end
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function read_moves(io)
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return [parse_move(line) for line in readlines(io)]
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end
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function apply_move(state, direction)
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if direction == 'U'
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state.head_y += 1
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elseif direction == 'D'
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state.head_y -= 1
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elseif direction == 'L'
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state.head_x -= 1
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elseif direction == 'R'
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state.head_x += 1
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elseif direction != 'O'
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throw(DomainError("Unknown direction"))
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end
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x_diff = state.head_x - state.tail_x
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y_diff = state.head_y - state.tail_y
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if abs(x_diff) <= 1 && abs(y_diff) <= 1
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return state
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end
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if abs(x_diff) <= 1
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state.tail_x += x_diff
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state.tail_y += sign(y_diff) * (abs(y_diff) - 1)
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elseif abs(y_diff) <= 1
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state.tail_y += y_diff
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state.tail_x += sign(x_diff) * (abs(x_diff) - 1)
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elseif abs(x_diff) == 2 && abs(y_diff) == 2
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# possible with more than 2 knots
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state.tail_x += sign(x_diff) * (abs(x_diff) - 1)
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state.tail_y += sign(y_diff) * (abs(y_diff) - 1)
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else
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throw(DomainError("invalid state " * string(state)))
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end
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return state
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end
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function get_visited(moves; npairs::Int=1)
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visited = Set{NTuple{2, Int}}()
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states = [KnotPair(0, 0, 0, 0) for _ in 1:npairs]
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push!(visited, (states[npairs].tail_x, states[npairs].tail_y))
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for move in moves
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for m in 1:move.count
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# println(move, " ", m)
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# print(" 1 ", states[1], " -> ")
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states[1] = apply_move(states[1], move.direction)
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# println(states[1])
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for i in 2:npairs
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states[i].head_x = states[i-1].tail_x
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states[i].head_y = states[i-1].tail_y
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# old_state = deepcopy(states[i])
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states[i] = apply_move(states[i], 'O')
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# if state_changed(states[i], old_state)
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# println(" ", i, " ", old_state, " -> ", states[i])
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# end
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end
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push!(visited, (states[npairs].tail_x, states[npairs].tail_y))
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end
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end
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return visited
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end
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function visited_map(visited)
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(min_x, max_x) = extrema([t[1] for t in visited])
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(min_y, max_y) = extrema([t[2] for t in visited])
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nrows = max_y - min_y + 1
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ncols = max_x - min_x + 1
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vmap = zeros(Int, nrows, ncols)
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for (x, y) in visited
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vmap[nrows - (y - min_y), (x - min_x + 1)] = 1
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end
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return vmap
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end
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function test()
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@testset "visited count 2 knot" verbose=true begin
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@test length(get_visited(read_moves("example.txt"))) == 13
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@test length(get_visited(read_moves("input.txt"))) == 6037
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end
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@testset "visited count 10 knot" verbose=true begin
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@test length(get_visited(read_moves("example.txt"), npairs=9)) == 1
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@test length(get_visited(read_moves("input.txt"), npairs=9)) == 2485
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end
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end
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function main()
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if size(ARGS, 1) == 0
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test()
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else
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infile = ARGS[1]
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println("infile = ", infile)
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moves = read_moves(infile)
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println("moves: ", moves)
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visited = get_visited(moves)
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println("visited: ", visited)
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println("count : ", length(visited))
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display(visited_map(visited))
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println()
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visited10 = get_visited(moves, npairs=9)
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println("visited10: ", visited10)
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println("count10 : ", length(visited10))
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display(visited_map(visited10))
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println()
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end
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end
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main()
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