45 lines
1.1 KiB
Lua
45 lines
1.1 KiB
Lua
#!/usr/bin/env lua
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map = {}
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for line in io.lines("input.txt") do
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x0, y0, x1, y1 = string.match(line, "(%d+),(%d+) .+ (%d+),(%d+)")
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x0 = tonumber(x0) x1 = tonumber(x1) y0 = tonumber(y0) y1 = tonumber(y1)
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if y0 > y1 then ystep = -1 else ystep = 1 end
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if x0 > x1 then xstep = -1 else xstep = 1 end
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if x0 == x1 then
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map[x0] = map[x0] or {}
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for y = y0, y1, ystep do
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map[x0][y] = (map[x0][y] or 0) + 1
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end
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elseif y0 == y1 then
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for x = x0, x1, xstep do
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map[x] = map[x] or {}
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map[x][y0] = (map[x][y0] or 0) + 1
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end
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else
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x = x0 y = y0
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while x ~= x1 and y ~= y1 do
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map[x] = map[x] or {}
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map[x][y] = (map[x][y] or 0) + 1
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x = x + xstep
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y = y + ystep
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end
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map[x] = map[x] or {}
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map[x][y] = (map[x][y] or 0) + 1
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end
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end
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intersections = 0
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for _, col in pairs(map) do
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for _, f in pairs(col) do
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if f > 1 then
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intersections = intersections + 1
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end
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end
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end
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print("Answer:", intersections)
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