tasks a-s

This commit is contained in:
Ingy döt Net 2013-04-10 23:57:08 -07:00
parent 47bf37c096
commit b83f433714
12433 changed files with 156208 additions and 123 deletions

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Consider some sequence of elements. (It differs from a mere set of elements by having an ordering among members.)
A ''subsequence'' contains some subset of the elements of this sequence, in the same order.
A ''continuous'' subsequence is one in which no elements are missing between the first and last elements of the subsequence.
Note: Subsequences are defined ''structurally'', not by their contents. So a sequence ''a,b,c,d'' will always have the same subsequences and continuous subsequences, no matter which values are substituted; it may even be the same value.
'''Task''': Find all non-continuous subsequences for a given sequence. Example: For the sequence ''1,2,3,4'', there are five non-continuous subsequences, namely ''1,3''; ''1,4''; ''2,4''; ''1,3,4'' and ''1,2,4''.
'''Goal''': There are different ways to calculate those subsequences. Demonstrate algorithm(s) that are natural for the language.

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---
note: Discrete math

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PROC test non continuous = VOID: BEGIN
MODE SEQMODE = CHAR;
MODE SEQ = [1:0]SEQMODE;
MODE YIELDSEQ = PROC(SEQ)VOID;
PROC gen ncs =
( SEQ tail, # To generate subsequences of #
SEQ head, # Already generated #
BOOL contiguous,# It is still continuous #
YIELDSEQ yield
) VOID:
BEGIN
IF NOT contiguous ANDTH UPB head > 1 THEN
yield (head)
FI;
IF UPB tail /= 0 THEN
[UPB head+1]SEQMODE new head;
new head [:UPB head] := head;
FOR i TO UPB tail DO
new head [UPB new head] := tail [i];
gen ncs
( tail[i + 1:UPB tail],
new head,
contiguous ANDTH (i = LWB tail OREL UPB head = 0),
yield
)
OD
FI
END # put ncs #;
# FOR SEQ seq IN # gen ncs(("a","e","i","o","u"), (), TRUE, # ) DO ( #
## (SEQ seq)VOID:
print((seq, new line))
# OD # )
END; test non continuous

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MODE SEQMODE = STRING;
MODE SEQ = [1:0]SEQMODE;
MODE YIELDSEQ = PROC(SEQ)VOID;
PROC gen ncs = (SEQ seq, YIELDSEQ yield)VOID:
BEGIN
IF UPB seq - 1 > bits width THEN stop FI;
[UPB seq]SEQMODE out; INT upb out;
BITS lim := 16r1 SHL UPB seq;
BITS upb k := lim SHR 1;
# assert(lim); #
BITS empty = 16r000000000; # const #
FOR j TO ABS lim-1 DO
INT state := 1;
BITS k1 := upb k;
WHILE k1 NE empty DO
BITS b := BIN j AND k1;
CASE state IN
# state 1 # IF b NE empty THEN state +:= 1 FI,
# state 2 # IF b EQ empty THEN state +:= 1 FI,
# state 3 #
BEGIN
IF b EQ empty THEN GO TO continue k1 FI;
upb out := 0;
BITS k2 := upb k; FOR i WHILE k2 NE empty DO
IF (BIN j AND k2) NE empty THEN out[upb out +:= 1] := seq[i] FI;
k2 := k2 SHR 1
OD;
yield(out[:upb out]);
k1 := empty # empty: ending containing loop #
END
ESAC;
continue k1: k1 := k1 SHR 1
OD
OD
END;
main:(
[]STRING seqs = ("a","e","i","o","u");
# FOR SEQ seq IN # gen ncs(seqs, # ) DO ( #
## (SEQ seq)VOID:
print((seq, new line))
# OD # )
)

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with Ada.Text_IO; use Ada.Text_IO;
procedure Test_Non_Continuous is
type Sequence is array (Positive range <>) of Integer;
procedure Put_NCS
( Tail : Sequence; -- To generate subsequences of
Head : Sequence := (1..0 => 1); -- Already generated
Contiguous : Boolean := True -- It is still continuous
) is
begin
if not Contiguous and then Head'Length > 1 then
for I in Head'Range loop
Put (Integer'Image (Head (I)));
end loop;
New_Line;
end if;
if Tail'Length /= 0 then
declare
New_Head : Sequence (Head'First..Head'Last + 1);
begin
New_Head (Head'Range) := Head;
for I in Tail'Range loop
New_Head (New_Head'Last) := Tail (I);
Put_NCS
( Tail => Tail (I + 1..Tail'Last),
Head => New_Head,
Contiguous => Contiguous and then (I = Tail'First or else Head'Length = 0)
);
end loop;
end;
end if;
end Put_NCS;
begin
Put_NCS ((1,2,3)); New_Line;
Put_NCS ((1,2,3,4)); New_Line;
Put_NCS ((1,2,3,4,5)); New_Line;
end Test_Non_Continuous;

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MsgBox % noncontinuous("a,b,c,d,e", ",")
MsgBox % noncontinuous("1,2,3,4", ",")
noncontinuous(list, delimiter)
{
stringsplit, seq, list, %delimiter%
n := seq0 ; sequence length
Loop % x := (1<<n) - 1 { ; try all 0-1 candidate sequences
If !RegExMatch(b:=ToBin(A_Index,n),"^0*1*0*$") { ; drop continuous subsequences
Loop Parse, b
t .= A_LoopField ? seq%A_Index% " " : "" ; position -> number
t .= "`n" ; new sequences in new lines
}
}
return t
}
ToBin(n,W=16) { ; LS W-bits of Binary representation of n
Return W=1 ? n&1 : ToBin(n>>1,W-1) . n&1
}

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DIM list1$(3)
list1$() = "1", "2", "3", "4"
PRINT "For [1, 2, 3, 4] non-continuous subsequences are:"
PROCnon_continuous_subsequences(list1$())
DIM list2$(4)
list2$() = "1", "2", "3", "4", "5"
PRINT "For [1, 2, 3, 4, 5] non-continuous subsequences are:"
PROCnon_continuous_subsequences(list2$())
END
DEF PROCnon_continuous_subsequences(l$())
LOCAL i%, j%, g%, n%, r%, s%, w%, a$, b$
n% = DIM(l$(),1)
FOR s% = 0 TO n%-2
FOR g% = s%+1 TO n%-1
a$ = "["
FOR i% = s% TO g%-1
a$ += l$(i%) + ", "
NEXT
FOR w% = 1 TO n%-g%
r% = n%+1-g%-w%
FOR i% = 1 TO 2^r%-1 STEP 2
b$ = a$
FOR j% = 0 TO r%-1
IF i% AND 2^j% b$ += l$(g%+w%+j%) + ", "
NEXT
PRINT LEFT$(LEFT$(b$)) + "]"
NEXT i%
NEXT w%
NEXT g%
NEXT s%
ENDPROC

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( ( noncontinuous
= sub
. ( sub
= su a nc
. !arg:(?su.?nc)
& !su
: %
%?a
( %:[%(sub$(!sjt.!nc !a))
| ?
& !nc:~
& out$(!nc !a)
& ~
)
)
& sub$(dummy !arg.)
|
)
& noncontinuous$(e r n i t)
);

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#include <assert.h>
#include <stdio.h>
int main(int c, char **v)
{
unsigned int n = 1 << (c - 1), i = n, j, k;
assert(n);
while (i--) {
if (!(i & (i + (i & -(int)i)))) // consecutive 1s
continue;
for (j = n, k = 1; j >>= 1; k++)
if (i & j) printf("%s ", v[k]);
putchar('\n');
}
return 0;
}

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#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
void binprint(unsigned int n, unsigned int m)
{
char c[sizeof(n) * 8 + 1];
int i = 0;
while (m >>= 1) c[i++] = n & m ? '#' : '-';
c[i] = 0;
puts(c);
}
int main(int c, char **v)
{
unsigned int n, gap, left, right;
if (c < 2 || ! (n = 1 << atoi(v[1]))) n = 16;
for (gap = 2; gap < n; gap <<= 1)
for (left = gap << 1; left < n; left |= left << 1)
for (right = 1; right < gap; right++)
binprint(left | right, n);
return 0;
}

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#include <stdio.h>
typedef unsigned char sint;
enum states { s_blnk = 0, s_tran, s_cont, s_disj };
/* Recursively look at each item in list, taking both choices of
picking the item or not. The state at each step depends on prvious
pickings, with the state transition table:
blank + no pick -> blank
blank + pick -> contiguous
transitional + no pick -> transitional
transitional + pick -> disjoint
contiguous + no pick -> transitional
contiguous + pick -> contiguous
disjoint + pick -> disjoint
disjoint + no pick -> disjoint
At first step, before looking at any item, state is blank.
Because state is known at each step and needs not be calculated,
it can be quite fast.
*/
unsigned char tbl[][2] = {
{ s_blnk, s_cont },
{ s_tran, s_disj },
{ s_tran, s_cont },
{ s_disj, s_disj },
};
void pick(sint n, sint step, sint state, char **v, unsigned long bits)
{
int i, b;
if (step == n) {
if (state != s_disj) return;
for (i = 0, b = 1; i < n; i++, b <<= 1)
if ((b & bits)) printf("%s ", v[i]);
putchar('\n');
return;
}
bits <<= 1;
pick(n, step + 1, tbl[state][0], v, bits); /* no pick */
pick(n, step + 1, tbl[state][1], v, bits | 1); /* pick */
}
int main(int c, char **v)
{
if (c - 1 >= sizeof(unsigned long) * 4)
printf("Too many items");
else
pick(c - 1, 0, s_blnk, v + 1, 0);
return 0;
}

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(use '[clojure.contrib.combinatorics :only (subsets)])
(defn of-min-length [min-length]
(fn [s] (>= (count s) min-length)))
(defn runs [c l]
(map (partial take l) (take-while not-empty (iterate rest c))))
(defn is-subseq? [c sub]
(some identity (map = (runs c (count sub)) (repeat sub))))
(defn non-continuous-subsequences [s]
(filter (complement (partial is-subseq? s)) (subsets s)))
(filter (of-min-length 2) (non-continuous-subsequences [:a :b :c :d]))

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is_contigous_binary = (n) ->
# return true if binary representation of n is
# of the form 1+0+
# examples:
# 0 true
# 1 true
# 100 true
# 110 true
# 1001 false
# 1010 false
# special case zero, or you'll get an infinite loop later
return true if n == 0
# first remove 0s from end
while n % 2 == 0
n = n / 2
# next, take advantage of the fact that a continuous
# run of 1s would be of the form 2^n - 1
is_power_of_two(n + 1)
is_power_of_two = (m) ->
while m % 2 == 0
m = m / 2
m == 1
seq_from_bitmap = (arr, n) ->
# grabs elements from array according to a bitmap
# e.g. if n == 13 (1101), and arr = ['a', 'b', 'c', 'd'],
# then return ['a', 'c', 'd'] (flipping bits to 1011, so
# that least significant bit comes first)
i = 0
new_arr = []
while n > 0
if n % 2 == 1
new_arr.push arr[i]
n -= 1
n /= 2
i += 1
new_arr
non_contig_subsequences = (arr) ->
# Return all subsqeuences from an array that have a "hole" in
# them. The order of the subsequences is not specified here.
# This algorithm uses binary counting, so it is limited to
# small lists, but large lists would be unwieldy regardless.
bitmasks = [0...Math.pow(2, arr.length)]
(seq_from_bitmap arr, n for n in bitmasks when !is_contigous_binary n)
arr = [1,2,3,4]
console.log non_contig_subsequences arr
for n in [1..10]
arr = [1..n]
num_solutions = non_contig_subsequences(arr).length
console.log "for n=#{n} there are #{num_solutions} solutions"

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> coffee non_contig_subseq.coffee
[ [ 1, 3 ],
[ 1, 4 ],
[ 2, 4 ],
[ 1, 2, 4 ],
[ 1, 3, 4 ] ]
for n=1 there are 0 solutions
for n=2 there are 0 solutions
for n=3 there are 1 solutions
for n=4 there are 5 solutions
for n=5 there are 16 solutions
for n=6 there are 42 solutions
for n=7 there are 99 solutions
for n=8 there are 219 solutions
for n=9 there are 466 solutions
for n=10 there are 968 solutions

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(defun all-subsequences (list)
(labels ((subsequences (tail &optional (acc '()) (result '()))
"Return a list of the subsequence designators of the
subsequences of tail. Each subsequence designator is a
list of tails of tail, the subsequence being the first
element of each tail."
(if (endp tail)
(list* (reverse acc) result)
(subsequences (rest tail) (list* tail acc)
(append (subsequences (rest tail) acc) result))))
(continuous-p (subsequence-d)
"True if the designated subsequence is continuous."
(loop for i in subsequence-d
for j on (first subsequence-d)
always (eq i j)))
(designated-sequence (subsequence-d)
"Destructively transforms a subsequence designator into
the designated subsequence."
(map-into subsequence-d 'first subsequence-d)))
(let ((nc-subsequences (delete-if #'continuous-p (subsequences list))))
(map-into nc-subsequences #'designated-sequence nc-subsequences))))

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(defun all-subsequences2 (list)
(labels ((recurse (s list)
(if (endp list)
(if (>= s 3)
'(())
'())
(let ((x (car list))
(xs (cdr list)))
(if (evenp s)
(append (mapcar (lambda (ys) (cons x ys))
(recurse (+ s 1) xs))
(recurse s xs))
(append (mapcar (lambda (ys) (cons x ys))
(recurse s xs))
(recurse (+ s 1) xs)))))))
(recurse 0 list)))

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import std.stdio;
T[][] ncsub(T)(in T[] seq, in int s=0) pure nothrow {
if (seq.length) {
T[][] aux;
foreach (ys; ncsub(seq[1..$], s + !(s % 2)))
aux ~= seq[0] ~ ys;
return aux ~ ncsub(seq[1..$], s + s % 2);
} else
return new T[][](s >= 3, 0);
}
void main() {
writeln(ncsub([1, 2, 3]));
writeln(ncsub([1, 2, 3, 4]));
foreach (nc; ncsub([1, 2, 3, 4, 5]))
writeln(nc);
}

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struct Ncsub(T) {
T[] seq;
int opApply(int delegate(ref int[]) dg) const {
immutable int n = seq.length;
int result;
auto S = new int[n];
FOR_I:
foreach (i; 1 .. 1 << seq.length) {
int len_S;
bool nc = false;
foreach (j; 0 .. seq.length + 1) {
immutable int k = i >> j;
if (k == 0) {
if (nc) {
auto auxS = S[0 .. len_S];
result = dg(auxS);
if (result)
break FOR_I;
}
break;
} else if (k % 2) {
S[len_S] = seq[j];
len_S++;
} else if (len_S)
nc = true;
}
}
return result;
}
}
void main() {
import std.array, std.range;
//assert(iota(24).array().Ncsub!int().walkLength() == 16_776_915);
auto r = array(iota(24));
int counter;
foreach (s; Ncsub!int(r))
counter++;
assert(counter == 16_776_915);
}

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package main
import "fmt"
const ( // state:
m = iota // missing: all elements missing so far
c // continuous: all elements included so far are continuous
cm // one or more continuous followed by one or more missing
cmc // non-continuous subsequence
)
func ncs(s []int) [][]int {
if len(s) < 3 {
return nil
}
return append(n2(nil, s[1:], m), n2([]int{s[0]}, s[1:], c)...)
}
var skip = []int{m, cm, cm, cmc}
var incl = []int{c, c, cmc, cmc}
func n2(ss, tail []int, seq int) [][]int {
if len(tail) == 0 {
if seq != cmc {
return nil
}
return [][]int{ss}
}
return append(n2(append([]int{}, ss...), tail[1:], skip[seq]),
n2(append(ss, tail[0]), tail[1:], incl[seq])...)
}
func main() {
ss := ncs([]int{1, 2, 3, 4})
fmt.Println(len(ss), "non-continuous subsequences:")
for _, s := range ss {
fmt.Println(" ", s)
}
}

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action p x = if p x then succ x else x
fenceM p q s [] = guard (q s) >> return []
fenceM p q s (x:xs) = do
(f,g) <- p
ys <- fenceM p q (g s) xs
return $ f x ys
ncsubseq = fenceM [((:), action even), (flip const, action odd)] (>= 3) 0

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continuous = null . dropWhile not . dropWhile id . dropWhile not
ncs xs = map (map fst . filter snd . zip xs) $
filter (not . continuous) $
mapM (const [True,False]) xs

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import Data.List
poset = foldr (\x p -> p ++ map (x:) p) [[]]
ncsubs [] = [[]]
ncsubs (x:xs) = tail $ nc [x] xs
where
nc [_] [] = [[]]
nc (_:x:xs) [] = nc [x] xs
nc xs (y:ys) = (nc (xs++[y]) ys) ++ map (xs++) (tail $ poset ys)

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import Data.List (subsequences, tails, delete)
disjoint a = concatMap (cutAt a) [1..length a - 2] where
cutAt s n = [a ++ b | b <- delete [] (subsequences right),
a <- init (tails left) ] where
(left, _:right) = splitAt n s
main = print $ length $ disjoint [1..20]

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import Data.List (inits, tails)
subseqs [] = []
subseqs (x:xs) = [x] : map (x:) s ++ s where s = subseqs xs
consecs x = concatMap (tail.inits) (tails x)
minus [] [] = []
minus (a:as) bb@(b:bs)
| a == b = minus as bs
| otherwise = a:minus as bb
disjoint s = (subseqs s) `minus` (consecs s)
main = mapM_ print $ disjoint [1..4]

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allmasks=: 2 #:@i.@^ #
firstend=:1 0 i.&1@E."1 ]
laststart=: 0 1 {:@I.@E."1 ]
noncont=: <@#~ (#~ firstend < laststart)@allmasks

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noncont 1+i.4
┌───┬───┬───┬─────┬─────┐
│2 4│1 4│1 3│1 3 4│1 2 4│
└───┴───┴───┴─────┴─────┘
noncont 'aeiou'
┌──┬──┬──┬───┬───┬──┬──┬───┬──┬───┬───┬────┬───┬───┬────┬────┐
│iu│eu│eo│eou│eiu│au│ao│aou│ai│aiu│aio│aiou│aeu│aeo│aeou│aeiu│
└──┴──┴──┴───┴───┴──┴──┴───┴──┴───┴───┴────┴───┴───┴────┴────┘
#noncont i.10
968

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contmasks=: a: ;@, 1 <:/~@i.&.>@i.@+ #
noncont=: <@#~ (allmasks -. contmasks)

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function non_continuous_subsequences(ary) {
var non_continuous = new Array();
for (var i = 0; i < ary.length; i++) {
if (! is_array_continuous(ary[i])) {
non_continuous.push(ary[i]);
}
}
return non_continuous;
}
function is_array_continuous(ary) {
if (ary.length < 2)
return true;
for (var j = 1; j < ary.length; j++) {
if (ary[j] - ary[j-1] != 1) {
return false;
}
}
return true;
}
load('json2.js'); /* http://www.json.org/js.html */
print(JSON.stringify( non_continuous_subsequences( powerset([1,2,3,4]))));

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GoodBad[i_List]:=Not[MatchQ[Differences[i],{1..}|{}]]
n=5
Select[Subsets[Range[n]],GoodBad]

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{{1,3},{1,4},{1,5},{2,4},{2,5},{3,5},{1,2,4},{1,2,5},{1,3,4},{1,3,5},{1,4,5},{2,3,5},{2,4,5},{1,2,3,5},{1,2,4,5},{1,3,4,5}}

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let rec fence s = function
[] ->
if s >= 3 then
[[]]
else
[]
| x :: xs ->
if s mod 2 = 0 then
List.map
(fun ys -> x :: ys)
(fence (s + 1) xs)
@
fence s xs
else
List.map
(fun ys -> x :: ys)
(fence s xs)
@
fence (s + 1) xs
let ncsubseq = fence 0

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declare
fun {NCSubseq SeqList}
Seq = {FS.value.make SeqList}
proc {Script Result}
%% the result is a subset of Seq
{FS.subset Result Seq}
%% at least one element of Seq is missing
local Gap in
{FS.include Gap Seq}
{FS.exclude Gap Result}
%% and this element is between the smallest
%% and the largest elements of the subsequence
Gap >: {FS.int.min Result}
Gap <: {FS.int.max Result}
end
%% enumerate all such sets
{FS.distribute naive [Result]}
end
in
{Map {SearchAll Script} FS.reflect.lowerBoundList}
end
in
{Inspect {NCSubseq [1 2 3 4]}}

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sub non_continuous_subsequences ( *@list ) {
powerset(@list).grep: { 1 != all( .[ 0 ^.. .end] Z- .[0 ..^ .end] ) }
}
sub powerset ( *@list ) {
reduce( -> @L, $n { [ @L, @L.map: {[ .list, $n ]} ] }, [[]], @list );
}
say ~ non_continuous_subsequences( 1..3 )».perl;
say ~ non_continuous_subsequences( 1..4 )».perl;
say ~ non_continuous_subsequences( ^4 ).map: {[<a b c d>[.list]].perl};

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my ($max, @current);
sub non_continuous {
my ($idx, $has_gap, $found) = @_;
for ($idx .. $max) {
push @current, $_;
# print "@current\n" if $has_gap; # uncomment for huge output
$found ++ if $has_gap;
$found += non_continuous($_ + 1, $has_gap) if $_ < $max;
pop @current;
$has_gap = @current; # don't set gap flag if it's empty still
}
$found;
}
$max = 20; # 1048365 sequences, 10 seconds-ish
print "found ", non_continuous(1), " sequences\n";

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(de ncsubseq (Lst)
(let S 0
(recur (S Lst)
(ifn Lst
(and (>= S 3) '(NIL))
(let (X (car Lst) XS (cdr Lst))
(ifn (bit? 1 S) # even
(conc
(mapcar '((YS) (cons X YS))
(recurse (inc S) XS) )
(recurse S XS) )
(conc
(mapcar '((YS) (cons X YS))
(recurse S XS) )
(recurse (inc S) XS) ) ) ) ) ) ) )

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define ncsubseq(l);
lvars acc = [], gap_started = false, is_continuous = true;
define do_it(l1, l2);
dlocal gap_started;
lvars el, save_is_continuous = is_continuous;
if l2 = [] then
if not(is_continuous) then
cons(l1, acc) -> acc;
endif;
else
front(l2) -> el;
back(l2) -> l2;
not(gap_started) and is_continuous -> is_continuous;
do_it(cons(el, l1), l2);
save_is_continuous -> is_continuous;
not(l1 = []) or gap_started -> gap_started;
do_it(l1, l2);
endif;
enddefine;
do_it([], rev(l));
acc;
enddefine;
ncsubseq([1 2 3 4 5]) =>

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[[1 3] [1 4] [2 4] [1 2 4] [1 3 4] [1 5] [2 5] [1 2 5] [3 5] [1 3 5]
[2 3 5] [1 2 3 5] [1 4 5] [2 4 5] [1 2 4 5] [1 3 4 5]]

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Function SubSequence ( [Array] $S, [Boolean] $all=$false )
{
$sc = $S.count
if( $sc -gt ( 2 - [Int32] $all ) ) {
[void] $sc--
0..$sc | ForEach-Object {
$gap = $_
"$( $S[ $_ ] )"
if( $gap -lt $sc )
{
SubSequence ( ( $gap + 1 )..$sc | Where-Object { $_ -ne $gap } ) ( ( $gap -ne 0 ) -or $all ) | ForEach-Object {
[String]::Join( ',', ( ( [String]$_ ).Split(',') | ForEach-Object {
$lt = $true
} {
if( $lt -and ( $_ -gt $gap ) )
{
$S[ $gap ]
$lt = $false
}
$S[ $_ ]
} {
if( $lt )
{
$S[ $gap ]
}
}
) )
}
}
}
#[String]::Join( ',', $S)
} else {
$S | ForEach-Object { [String] $_ }
}
}
Function NonContinuous-SubSequence ( [Array] $S )
{
$sc = $S.count
if( $sc -eq 3 )
{
[String]::Join( ',', $S[ ( 0,2 ) ] )
} elseif ( $sc -gt 3 ) {
[void] $sc--
$gaps = @()
$gaps += ( ( NonContinuous-SubSequence ( 1..$sc ) ) | ForEach-Object {
$gap1 = ",$_,"
"0,{0}" -f ( [String]::Join( ',', ( 1..$sc | Where-Object { $gap1 -notmatch "$_," } ) ) )
} )
$gaps += 1..( $sc - 1 )
2..( $sc - 1 ) | ForEach-Object {
$gap2 = $_ - 1
$gaps += ( ( SubSequence ( $_..$sc ) ) | ForEach-Object {
"$gap2,$_"
} )
}
#Write-Host "S $S gaps $gaps"
$gaps | ForEach-Object {
$gap3 = ",$_,"
"$( 0..$sc | Where-Object { $gap3 -notmatch ",$_," } | ForEach-Object {
$S[$_]
} )" -replace ' ', ','
}
} else {
$null
}
}
( NonContinuous-SubSequence 'a','b','c','d','e' ) | Select-Object length, @{Name='value';Expression={ $_ } } | Sort-Object length, value | ForEach-Object { $_.value }

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% fetch all the subsequences
ncsubs(L, LNCSL) :-
setof(NCSL, one_ncsubs(L, NCSL), LNCSL).
% how to build one subsequence
one_ncsubs(L, NCSL) :-
extract_elem(L, NCSL);
( sublist(L, L1),
one_ncsubs(L1, NCSL)).
% extract one element of the list
% this element is neither the first nor the last.
extract_elem(L, NCSL) :-
length(L, Len),
Len1 is Len - 2,
between(1, Len1, I),
nth0(I, L, Elem),
select(Elem, L, NCS1),
( NCSL = NCS1; extract_elem(NCS1, NCSL)).
% extract the first or the last element of the list
sublist(L, SL) :-
(L = [_|SL];
reverse(L, [_|SL1]),
reverse(SL1, SL)).

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?- ncsubs([a,e,i,o,u], L).
L = [[a,e,i,u],[a,e,o],[a,e,o,u],[a,e,u],[a,i],[a,i,o],[a,i,o,u],[a,i,u],[a,o],[a,o,u],[a,u],[e,i,u],[e,o],[e,o,u],[e,u],[i,u]]

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def ncsub(seq, s=0):
if seq:
x = seq[:1]
xs = seq[1:]
p2 = s % 2
p1 = not p2
return [x + ys for ys in ncsub(xs, s + p1)] + ncsub(xs, s + p2)
else:
return [[]] if s >= 3 else []

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from sys import argv
import psyco
def C(n, k):
result = 1
for d in xrange(1, k+1):
result *= n
n -= 1
result /= d
return result
# http://oeis.org/A002662
nsubs = lambda n: sum(C(n, k) for k in xrange(3, n+1))
def ncsub(seq):
n = len(seq)
result = [None] * nsubs(n)
pos = 0
for i in xrange(1, 2 ** n):
S = []
nc = False
for j in xrange(n + 1):
k = i >> j
if k == 0:
if nc:
result[pos] = S
pos += 1
break
elif k % 2:
S.append(seq[j])
elif S:
nc = True
return result
from sys import argv
import psyco
psyco.full()
n = 10 if len(argv) < 2 else int(argv[1])
print len( ncsub(range(1, n)) )

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ncsub <- function(x)
{
n <- length(x)
a <- seq_len(n)
seqlist <- list()
for(i in 2:(n-1))
{
seqs <- combn(a, i) # Get all subseqs
ok <- apply(seqs, 2, function(x) any(diff(x)!=1)) # Find noncts ones
newseqs <- unlist(apply(seqs[,ok], 2, function(x) list(x)), recursive=FALSE) # Convert matrix to list of its columns
seqlist <- c(seqlist, newseqs) # Append to existing list
}
lapply(seqlist, function(index) x[index])
}
# Example usage
ncsub(1:4)
ncsub(letters[1:5])

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/*REXX program to list non-continuous subsequences (NCS), given a seq.*/
parse arg list /*the the list from the CL.*/
if list='' then list=1 2 3 4 5 /*Specified? Use default. */
say 'list=' space(list); say /*show list to the terminal*/
w=words(list) ; #=0 /*# words in list; # of NCS*/
$=left(123456789,w) /*build a string of digits.*/
tail=right($,max(0,w-2)) /*construct a "fast" tail. */
do j=13 to left($,1) || tail /*step through the list. */
if verify(j,$)\==0 then iterate /*Not one of the chosen? */
f=left(j,1) /*the first digit of j. */
NCS=0 /*not non-continuous subseq*/
do k=2 to length(j); _=substr(j,k,1) /*pick off a single digit. */
if _ <= f then iterate j /*if next digit ≤ then skip*/
if _ \== f+1 then NCS=1 /*it's OK as of now. */
f=_ /*we now got a new next dig*/
end /*k*/
if \NCS then iterate /*¬OK? Then skip this num.*/
#=#+1 /*Eureka! We found one. */
x= /*the beginning of the NCS.*/
do m=1 for length(j) /*build a thingy to display*/
x=x word(list,substr(j,m,1)) /*pick off a number to show*/
end /*m*/
say 'a non-continuous subsequence: ' x /*show a non-cont. subseq. */
end /*j*/
if #==0 then #='no' /*make it more gooder Eng. */
say; say # "non-continuous subsequence"s(#) 'were found.'
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────S subroutine───────────────────────*/
s: if arg(1)==1 then return ''; return word(arg(2) 's',1) /*plurals.*/

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class Array
def func_power_set
inject([[]]) { |ps,item| # for each item in the Array
ps + # take the powerset up to now and add
ps.map { |e| e + [item] } # it again, with the item appended to each element
}
end
def non_continuous_subsequences
func_power_set.find_all {|seq| not seq.continuous}
end
def continuous
each_cons(2) {|a, b| return false if a+1 != b}
true
end
end
p (1..3).to_a.non_continuous_subsequences
p (1..4).to_a.non_continuous_subsequences
p (1..5).to_a.non_continuous_subsequences

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(define (ncsubseq lst)
(let recurse ((s 0)
(lst lst))
(if (null? lst)
(if (>= s 3)
'(())
'())
(let ((x (car lst))
(xs (cdr lst)))
(if (even? s)
(append
(map (lambda (ys) (cons x ys))
(recurse (+ s 1) xs))
(recurse s xs))
(append
(map (lambda (ys) (cons x ys))
(recurse s xs))
(recurse (+ s 1) xs)))))))

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fun fence s [] =
if s >= 3 then
[[]]
else
[]
| fence s (x :: xs) =
if s mod 2 = 0 then
map
(fn ys => x :: ys)
(fence (s + 1) xs)
@
fence s xs
else
map
(fn ys => x :: ys)
(fence s xs)
@
fence (s + 1) xs
fun ncsubseq xs = fence 0 xs

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proc subsets l {
set res [list [list]]
foreach e $l {
foreach subset $res {lappend res [lappend subset $e]}
}
return $res
}
proc is_not_continuous seq {
set last [lindex $seq 0]
foreach e [lrange $seq 1 end] {
if {$e-1 != $last} {return 1}
set last $e
}
return 0
}
proc lfilter {f list} {
set res {}
foreach i $list {if [$f $i] {lappend res $i}}
return $res
}
% lfilter is_not_continuous [subsets {1 2 3 4}]
{1 3} {1 4} {2 4} {1 2 4} {1 3 4}

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#import std
noncontinuous = num; ^rlK3ZK17rSS/~& powerset
#show+
examples = noncontinuous 'abcde'