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local monkeys = {}
local f = assert(io.open(arg[1], "r"))
for line in f:lines() do
local n, r = line:match("(%a+): (.*)$")
local le, op, ri = r:match("(%a+) (.) (%a+)")
if le == nil then
local val = tonumber(r)
monkeys[n] = {val=val}
else
monkeys[n] = {l = le, op = op, r = ri}
end
end
function order(monkeys)
local todo = {}
local history = {}
-- start at root.
table.insert(todo, "root")
table.insert(history, "root")
while true do
local cur = table.remove(todo, 1) -- queue
if cur == nil then break end
if monkeys[cur].val == nil then
table.insert(todo, monkeys[cur].l)
table.insert(todo, monkeys[cur].r)
table.insert(history, monkeys[cur].l)
table.insert(history, monkeys[cur].r)
end
end
return history
end
function calc(monkeys, ordered)
-- now step through in order filling in vals.
for i=#ordered,1,-1 do
local cur = ordered[i]
if monkeys[cur].val == nil then
local l = monkeys[monkeys[cur].l].val
local r = monkeys[monkeys[cur].r].val
local op = monkeys[cur].op
assert(l); assert(r)
local ans
if op == '+' then
ans = l + r
elseif op == '-' then
ans = l - r
elseif op == '/' then
ans = l / r
elseif op == '*' then
ans = l * r
end
monkeys[cur].val = ans
end
end
return monkeys.root.val
end
local hist = order(monkeys)
print(calc(monkeys, hist))
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