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|
#!/opt/local/bin/lua
--
-- See ../README.md
--
--
-- Run as: lua ch-2.lua < input-file
--
local SIZE = 7
for line in io . lines () do
local numbers = {}
for n in line : gmatch ("-?%d+") do
numbers [#numbers + 1] = tonumber (n)
end
--
-- Initialize the a differences table.
--
local differences = {}
for n_i, n in pairs (numbers) do
differences [n] = {}
end
--
-- Find all the differences; store the indices of the
-- pairs of numbers giving the difference. Ignore a difference
-- which is not present in the numbers array.
--
for i = 1, SIZE do
for j = i + 1, SIZE do
local diff = numbers [i] - numbers [j]
if differences [ diff] ~= nil
then table . insert (differences [ diff], {i, j})
end
if differences [-diff] ~= nil
then table . insert (differences [-diff], {j, i})
end
end
end
--
-- For each possible value d, find the pairs of differences
-- equal to d, such that all five numbers are difference.
--
for d_i = 1, SIZE do
local d = numbers [d_i]
local diffs = differences [d]
for x = 1, #diffs do
--
-- Ignore any difference involving d_i
--
if diffs [x] [1] == d_i or diffs [x] [2] == d_i
then goto end_x
end
for y = x + 1, #diffs do
--
-- Second difference cannot involve the number at d_i,
-- and the indices involved in the second difference
-- must be different from the first difference.
--
if diffs [y] [1] == d_i or diffs [y] [2] == d_i or
diffs [x] [1] == diffs [y] [1] or
diffs [x] [1] == diffs [y] [2] or
diffs [x] [2] == diffs [y] [1] or
diffs [x] [2] == diffs [y] [2]
then goto end_y
end
--
-- W.l.o.g. we can now assume diffs [x] are
-- the indices for a and c, and diffs [y]
-- are the indices for g and e.
--
local a_i = diffs [x] [1]
local c_i = diffs [x] [2]
local g_i = diffs [y] [1]
local e_i = diffs [y] [2]
--
-- Try the remaining indices for b_i and f_i
--
for b_i = 1, SIZE do
if b_i == a_i or b_i == c_i or b_i == d_i or
b_i == e_i or b_i == g_i
then goto end_bi
end
for f_i = 1, SIZE do
if f_i == a_i or f_i == b_i or f_i == c_i or
f_i == d_i or f_i == e_i or f_i == g_i
then goto end_fi
end
--
-- Do we have a winner?
--
local target = numbers [a_i] + numbers [b_i]
if target == numbers [b_i] + numbers [c_i] +
numbers [d_i] and
target == numbers [d_i] + numbers [e_i] +
numbers [f_i] and
target == numbers [f_i] + numbers [g_i]
then --
-- We have a winner. Print it, and its reverse
--
io . write (
string . format ("%d %d %d %d %d %d %d\n",
numbers [a_i], numbers [b_i],
numbers [c_i], numbers [d_i],
numbers [e_i], numbers [f_i],
numbers [g_i]))
io . write (
string . format ("%d %d %d %d %d %d %d\n",
numbers [g_i], numbers [f_i],
numbers [e_i], numbers [d_i],
numbers [c_i], numbers [b_i],
numbers [a_i]))
end
::end_fi::
end
::end_bi::
end
::end_y::
end
::end_x::
end
end
end
|
