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day3-2.lua
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day3-2.lua
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io.input( "day3-input.txt" )
io.write( "Please enter your puzzle input: \n" )
local input = tonumber( string.match( io.read(), "%d+" ) )
local direction
local function turnLeft()
if direction.x == 1 then
direction = { x = 0, y = 1 }
elseif direction.y == 1 then
direction = { x = -1, y = 0 }
elseif direction.x == -1 then
direction = { x = 0, y = -1 }
elseif direction.y == -1 then
direction = { x = 1, y = 0 }
end
end
local x = 0
local y = 0
local size = 1
local leg = 1
local step = 0
local sum = 0
local memory = { [ 0 ] = { [ 0 ] = 1 } }
direction = { x = 1, y = 0 }
while not ( sum > input ) do
x = x + direction.x
y = y + direction.y
step = step + 1
if step == size then
turnLeft()
if leg == 1 then
leg = 2
elseif leg == 2 then
size = size + 1
leg = 1
end
step = 0
end
sum = 0
for xPos = x - 1, x + 1 do
for yPos = y - 1, y + 1 do
if memory[ xPos ] and memory[ xPos ][ yPos ] then
sum = sum + memory[ xPos ][ yPos ]
end
end
end
if not memory[ x ] then
memory[ x ] = {}
end
memory[ x ][ y ] = sum
-- print( x, y, sum )
end
--[[
-- print out the memory. a bit inefficient because the table dimensions are in the opposite order that they're printed
for yPos = 10, -10, -1 do
for xPos = -10, 10 do
if memory[ xPos ] and memory[ xPos ][ yPos ] then
io.write( tostring( memory[ xPos ][ yPos ] ), "\t" )
end
end
io.write( "\n" )
end
]]
io.write( memory[ x ][ y ], " is the first value written larger than ", input )