How to resolve the algorithm 100 doors step by step in the AppleScript programming language
How to resolve the algorithm 100 doors step by step in the AppleScript programming language
Table of Contents
Problem Statement
There are 100 doors in a row that are all initially closed.
You make 100 passes by the doors.
The first time through, visit every door and toggle the door (if the door is closed, open it; if it is open, close it).
The second time, only visit every 2nd door (door #2, #4, #6, ...), and toggle it.
The third time, visit every 3rd door (door #3, #6, #9, ...), etc, until you only visit the 100th door.
Answer the question: what state are the doors in after the last pass? Which are open, which are closed?
Alternate:
As noted in this page's discussion page, the only doors that remain open are those whose numbers are perfect squares.
Opening only those doors is an optimization that may also be expressed;
however, as should be obvious, this defeats the intent of comparing implementations across programming languages.
Let's start with the solution:
Step by Step solution about How to resolve the algorithm 100 doors step by step in the AppleScript programming language
Source code in the applescript programming language
set is_open to {}
repeat 100 times
set end of is_open to false
end
repeat with pass from 1 to 100
repeat with door from pass to 100 by pass
set item door of is_open to not item door of is_open
end
end
set open_doors to {}
repeat with door from 1 to 100
if item door of is_open then
set end of open_doors to door
end
end
set text item delimiters to ", "
display dialog "Open doors: " & open_doors
on _100doors()
script o
property doors : {}
end script
repeat 100 times
set end of o's doors to false -- false = "not open".
end repeat
repeat with pass from 1 to 100
if (not item pass of o's doors) then set item pass of o's doors to pass
repeat with d from (pass + pass) to 100 by pass
set item d of o's doors to (not item d of o's doors)
end repeat
end repeat
return o's doors's integers
end _100doors
on join(lst, delim)
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to delim
set txt to lst as text
set AppleScript's text item delimiters to astid
return txt
end join
return "Open doors:
" & join(_100doors(), ", ")
"Open doors:
1, 4, 9, 16, 25, 36, 49, 64, 81, 100"
-- FINAL DOOR STATES ---------------------------------------------------------
-- finalDoors :: Int -> [(Int, Bool)]
on finalDoors(n)
-- toggledCorridor :: [(Int, Bool)] -> (Int, Bool) -> Int -> [(Int, Bool)]
script toggledCorridor
on |λ|(a, _, k)
-- perhapsToggled :: Bool -> Int -> Bool
script perhapsToggled
on |λ|(x, i)
if i mod k = 0 then
{i, not item 2 of x}
else
{i, item 2 of x}
end if
end |λ|
end script
map(perhapsToggled, a)
end |λ|
end script
set xs to enumFromTo(1, n)
foldl(toggledCorridor, ¬
zip(xs, replicate(n, {false})), xs)
end finalDoors
-- TEST ----------------------------------------------------------------------
on run
-- isOpenAtEnd :: (Int, Bool) -> Bool
script isOpenAtEnd
on |λ|(door)
(item 2 of door)
end |λ|
end script
-- doorNumber :: (Int, Bool) -> Int
script doorNumber
on |λ|(door)
(item 1 of door)
end |λ|
end script
map(doorNumber, filter(isOpenAtEnd, finalDoors(100)))
--> {1, 4, 9, 16, 25, 36, 49, 64, 81, 100}
end run
-- GENERIC FUNCTIONS ---------------------------------------------------------
-- enumFromTo :: Int -> Int -> [Int]
on enumFromTo(m, n)
if n < m then
set d to -1
else
set d to 1
end if
set lst to {}
repeat with i from m to n by d
set end of lst to i
end repeat
return lst
end enumFromTo
-- filter :: (a -> Bool) -> [a] -> [a]
on filter(f, xs)
tell mReturn(f)
set lst to {}
set lng to length of xs
repeat with i from 1 to lng
set v to item i of xs
if |λ|(v, i, xs) then set end of lst to v
end repeat
return lst
end tell
end filter
-- foldl :: (a -> b -> a) -> a -> [b] -> a
on foldl(f, startValue, xs)
tell mReturn(f)
set v to startValue
set lng to length of xs
repeat with i from 1 to lng
set v to |λ|(v, item i of xs, i, xs)
end repeat
return v
end tell
end foldl
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
tell mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to |λ|(item i of xs, i, xs)
end repeat
return lst
end tell
end map
-- min :: Ord a => a -> a -> a
on min(x, y)
if y < x then
y
else
x
end if
end min
-- Lift 2nd class handler function into 1st class script wrapper
-- mReturn :: Handler -> Script
on mReturn(f)
if class of f is script then
f
else
script
property |λ| : f
end script
end if
end mReturn
-- replicate :: Int -> a -> [a]
on replicate(n, a)
set out to {}
if n < 1 then return out
set dbl to {a}
repeat while (n > 1)
if (n mod 2) > 0 then set out to out & dbl
set n to (n div 2)
set dbl to (dbl & dbl)
end repeat
return out & dbl
end replicate
-- zip :: [a] -> [b] -> [(a, b)]
on zip(xs, ys)
set lng to min(length of xs, length of ys)
set lst to {}
repeat with i from 1 to lng
set end of lst to {item i of xs, item i of ys}
end repeat
return lst
end zip
{1, 4, 9, 16, 25, 36, 49, 64, 81, 100}
map(factorCountMod2, enumFromTo(1, 100))
on factorCountMod2(n)
{n, (length of integerFactors(n)) mod 2 = 1}
end factorCountMod2
-- perfectSquaresUpTo :: Int -> [Int]
on perfectSquaresUpTo(n)
script squared
-- (Int -> Int)
on |λ|(x)
x * x
end |λ|
end script
set realRoot to n ^ (1 / 2)
set intRoot to realRoot as integer
set blnNotPerfectSquare to not (intRoot = realRoot)
map(squared, enumFromTo(1, intRoot - (blnNotPerfectSquare as integer)))
end perfectSquaresUpTo
on run
perfectSquaresUpTo(100)
end run
{1, 4, 9, 16, 25, 36, 49, 64, 81, 100}
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