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local Report = {}
Report.__index = Report
function Report:__tostring ()
return table.concat(self, ' ')
end
function Report:new (values)
if #values == 0 then error 'Cannot construct an empty report.' end
setmetatable(values, Report)
return values
end
function Report:is_safe_dir (down, allow_dampen)
local function valid_jump (start, finish)
local diff = down and start - finish or finish - start
return diff >= 1 and diff <= 3
end
local prev = self[1]
for i = 2,#self do
local cur = self[i]
if valid_jump(prev, cur) then
prev = cur
elseif not allow_dampen then
return false
else
local remove_cur = i == #self or valid_jump(prev, self[i+1])
if not remove_cur then
local remove_prev = i == 2 or valid_jump(self[i-2], cur)
if not remove_prev then return false end
prev = cur
end
allow_dampen = false
end
end
return true
end
function Report:is_safe (allow_dampen)
return self:is_safe_dir(true, allow_dampen) or
self:is_safe_dir(false, allow_dampen)
end
local input = {}
for line in function () return io.read('*l') end do
local parsed = {}
for v in line:gmatch('%d+') do
table.insert(parsed, tonumber(v))
end
table.insert(input, Report:new(parsed))
end
function input:sum_safe (allow_dampen)
local sum = 0
for _, x in ipairs(input) do
if x:is_safe(allow_dampen) then sum = sum + 1 end
end
return sum
end
function input:part1 ()
print(self)
print(self:sum_safe(false))
end
function input:part2 ()
print(self:sum_safe(true))
end
return input
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