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local knots, tail_moved = {}, {}
for i = 1,10 do table.insert(knots,{1,1}) end
local directions = {
R = {1,0},
U = {0,1},
L = {-1,0},
D = {0,-1},
}
local sfmt = "%d - %d"
local motion = {}
for i = -2,2 do
for j = -2, 2 do
if math.abs(i)^2 + math.abs(j)^2 > 2 then
motion[sfmt:format(i,j)] = {
i == 0 and 0 or math.abs(i)/i,
j == 0 and 0 or math.abs(j)/j
}
else
motion[sfmt:format(i,j)] = {0,0}
end
end
end
local function insert_tail_pos()
local tail = knots[#knots]
tail_moved[string.format(sfmt,tail[1],tail[2])] = true
end
local function move_knot(knot,twords)
local x,y = twords[1] - knot[1], twords[2] - knot[2]
local direction = motion[string.format("%d - %d",x,y)]
knot[1],knot[2] = knot[1] + direction[1], knot[2] + direction[2]
end
insert_tail_pos()
for line in io.lines() do
local direction, steps = line:match("([RULD]) (%d+)")
direction = directions[direction]
for i = 1,steps do
knots[1][1], knots[1][2] = knots[1][1] + direction[1], knots[1][2] + direction[2]
for j = 2,#knots do
move_knot(knots[j],knots[j-1])
insert_tail_pos()
end
end
end
local tmr = {}
for p,_ in pairs(tail_moved) do
table.insert(tmr,p)
end
print(#tmr)
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