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#!/usr/bin/env lua
--[[
Challenge 101
TASK #1 � Pack a Spiral
Submitted by: Stuart Little
You are given an array @A of items (integers say, but they can be anything).
Your task is to pack that array into an MxN matrix spirally counterclockwise,
as tightly as possible.
�Tightly� means the absolute value |M-N| of the difference has to be as small
as possible.
--]]
-- find out m,n
function smallest_rect(n)
local low = 1
local high = n
for i=1, math.floor(math.sqrt(n)) do
if math.floor(math.fmod(n, i)) == 0 then
low, high = i, math.floor(n/i)
end
end
return low, high
end
-- find max width of elements, convert to int
function max_width(numbers)
local num_width = 1
for i=1, #numbers do
if #numbers[i] < num_width then
num_width = #numbers[i]
numbers[i] = tonumber(numbers[i])
end
end
return num_width
end
-- build empty rectangle
function build_empty_rectangle(m, n)
local rect = {}
for r=1, m do
rect[r] = {}
for c=1, n do
rect[r][c] = ""
end
end
return rect
end
-- build spiral rectangle
function spiral(numbers)
local m, n = smallest_rect(#numbers)
local num_width = max_width(numbers)
local rect = build_empty_rectangle(m, n)
local r, c = m, 1
local i = 1
while i <= #numbers do
-- go East
while c <= n do
if rect[r][c] ~= "" then break end
rect[r][c] = string.format("%"..tostring(num_width+1).."d",
numbers[i])
i = i + 1
c = c + 1
end
c = c - 1
r = r - 1
-- go North
while r >= 1 do
if rect[r][c] ~= "" then break end
rect[r][c] = string.format("%"..tostring(num_width+1).."d",
numbers[i])
i = i + 1
r = r - 1
end
r = r + 1
c = c - 1
-- go West
while c >= 1 do
if rect[r][c] ~= "" then break end
rect[r][c] = string.format("%"..tostring(num_width+1).."d",
numbers[i])
i = i + 1
c = c - 1
end
c = c + 1
r = r + 1
-- go South
while r <= m do
if rect[r][c] ~= "" then break end
rect[r][c] = string.format("%"..tostring(num_width+1).."d",
numbers[i])
i = i + 1
r = r + 1
end
r = r - 1
c = c + 1
end
-- print result
for r=1, m do
for c=1, n do
io.write(rect[r][c])
end
io.write("\n")
end
end
spiral(arg)
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