Sorting lists

Question

I'm trying to sort a set of 4 lists that depend on each other. I'm using a bubble-sort to do this. I sort one list and when I need to swap items I also swap the corresponding items in the other three lists to keep them all synced.
So far I've only done this using a set of short lists. I've calculated that in order to sort the entire data-set using my bubble-sort will require about 20hrs (roughly 8000 items in each list).
I've looked into Database Events but it doesn't seem to have a sort function. I found a quick-sort routine on the web, but the code lacks comments and thus makes no sense to me.
Anybody know of a faster way to sort?
Message was edited by: Mausy

Answer 1

Hello
You may try a flavour of merge sort handler, which is stable (i.e. preserves original order of items with the same key) and has N * log N complexity in both average and the worst case.
(Quick sort is not stable and has N * N complexity in the worst case.)
Notes about the script.
In brief,
0) given a list of keys (= kk) and a list of values (= aa);
1) create a list of indices (= ii) to identify each value in original aa;
2) transpose {kk, ii} and build a list (= xx) of which element is {kk's item j, ii's item j} for i from 1 to count kk;
3) sort xx by its element's first item;
4) transpose xx and get sorted kk and sorted ii by key;
5) bulid sorted value list (= aa1) by extracting items from aa by using sorted indices sequentially.
(You can build sorted value list from other value list by using the same sorted indices sequentialy)
There're three essential handlers: cmp(), msort() and transpose().
The cmp() is comparator for msort() and cmp(x, y) returns true iff element x and y are out of order.
The msort() is non-recursive merge sort handler. (I made it non-recursive to avoid stack-overflow in AppleScript)
The transpose() is 2d-array transposer.
Hope you get the picture.
Good luck,
H
--SCRIPT
test()
on test()
script o
property kk : {} -- key list
property ii : {} -- index list
property aa : {} -- value list
property aa1 : {} -- value list sorted by key
set h to 100 -- test list size
-- make key list
repeat with i from 1 to h
set end of my kk to random number from 0 to (h div 2)
end repeat
set kk0 to kk's contents -- save original key list
-- make index list
repeat with i from 1 to count my kk
set end of my ii to i
end repeat
-- make value list
repeat with i from 1 to count my kk
set end of my aa to "a" & i
end repeat
-- sort list of (key & index) pair by key
set xx to transpose({kk, ii}) -- transpose
msort(xx, my cmp) -- sort
set {kk, ii} to transpose(xx) -- transpose back
-- retrieve values by sorted indices
repeat with i in my ii
set end of my aa1 to my aa's item i
end repeat
return {original_keys:kk0, sorted_keys:kk, sortedindices_bykey:ii, sortedvalues_bykey:aa1}
end script
tell o to run
end test
on cmp(x, y) -- comparator for msort handler
(* sort in ascending order of 1st item of list element *)
return x's item 1 > y's item 1
end cmp
on cmp(y, x) -- comparator for msort handler
(* sort in descending order of 1st item of list element *)
return x's item 1 > y's item 1
end cmp
on msort(aa, cmp_) -- v1.2f1
Basic non-recursive merge sort handler
having list sorted in place in ascending order.
list aa : list to be sorted in place
handler cmp_ : comparator
* cmp(x, y) must return true iff list element x and y are out of order.
script o
property xx : aa -- to be sorted in place
property xxl : count my xx
property yy : {}
property cmp : cmp_
on merge(p, q, r)
property xx: source list -- [*1]
integer p, q, r : absolute indices to specify range to be merged such that
xx's items p thru r is the target range,
xx's items p thru (q-1) is the first sublist already sorted (in ascending order) and
xx's items q thru r is the second sublist already sorted (in ascending order).
(p < q <= r)
Notes
[1] It assumes that xx[p, q-1] and xx[q, r] have been already sorted (p < q <= r).
Also xx is modified in place.
local i, j, k, xp, xr, yi, yj, ix, jx
if r - p = 1 then
set xp to my xx's item p
set xr to my xx's item r
if my cmp(xp, xr) then
set my xx's item p to xr
set my xx's item r to xp
end if
return -- exit
end if
if my cmp(my xx's item (q - 1), my xx's item q) then
else -- xx[p, q-1] & xx[q, r] are already sorted
return
end if
set yy to my xx's items p thru r -- working copy for comparison
set ix to q - p
set jx to r - p + 1
set i to 1
set j to q - p + 1
set k to p
set yi to my yy's item i
set yj to my yy's item j
repeat
if my cmp(yi, yj) then
set my xx's item k to yj
set j to j + 1
set k to k + 1
if j > jx then
set my xx's item k to yi
set i to i + 1
set k to k + 1
repeat until k > r
set my xx's item k to my yy's item i
set i to i + 1
set k to k + 1
end repeat
return
end if
set yj to my yy's item j
else
set my xx's item k to yi
set i to i + 1
set k to k + 1
if i > ix then
set my xx's item k to yj
set j to j + 1
set k to k + 1
repeat until k > r
set my xx's item k to my yy's item j
set j to j + 1
set k to k + 1
end repeat
return
end if
set yi to my yy's item i
end if
end repeat
end merge
on cmp(x, y)
(* default comparator for sort in ascending order (used if cmp_ = {}) *)
return x > y
end cmp
local d, i, j
if xxl ≤ 1 then return
if cmp_ = {} then set my cmp to cmp
set d to 2
repeat until d > xxl
repeat with i from 1 to (xxl - d + 1) by d
my merge(i, i + d div 2, i + d - 1)
end repeat
set i to i + d
set j to i + d div 2
if j ≤ xxl then my merge(i, j, xxl)
set d to d * 2
end repeat
if i ≤ xxl then my merge(1, i, xxl)
end script
tell o to run
end msort
on transpose(dd)
list dd: two dimentional array. e.g. {{11, 12}, {21, 22}, {31, 32}}
return list: transposed array. e.g. {{11, 21, 31}, {12, 22, 32}}
extra e.g.
{{1, 2, 3}} -> {{1}, {2}, {3}} [or {1, 2, 3} -> {{1, 2, 3}} -> {{1}, {2}, {3}}],
{{1}, {2}, {3}} -> {{1, 2, 3}}
script o
property aa : dd
property xx : {}
property yy : {}
local n
if my aa is {} then return {}
if my aa's item 1's class is not list then set my aa to {my aa} -- as (1,n) array
set n to my aa's item 1's length
repeat with a in my aa
if (count a) is not n then error "lists' lengths mismatch" number 8008
end repeat
repeat with i from 1 to n
set my xx to {}
repeat with a in my aa
set end of my xx to a's item i
end repeat
set end of my yy to my xx
end repeat
return my yy's contents
end script
tell o to run
end transpose
--END OF SCRIPT
Message was edited by: Hiroto