# Can you Golf Golf?

You are required to generate a random 18-hole golf course.

Example output:

[3 4 3 5 5 4 4 4 5 3 3 4 4 3 4 5 5 4]


Rules:

• Your program must output a list of hole lengths for exactly 18 holes
• Each hole must have a length of 3, 4 or 5
• The hole lengths must add up to 72 for the entire course
• Your program must be able to produce every possible hole configuration with some non-zero-probability (the probabilities of each configuration need not be equal, but feel free to claim extra kudos if this is the case)
• Please confirm, 44152809 solutions? Sep 26, 2012 at 0:38
• I too am curious on the exact number of solutions, however I think it should be more than 44 million... (I am no mathmetician, however: | 1(5)/1(3) = 306 possibilities (17*18) | 2(5)/2(3) = 69360 poss (17*17*16*15) | 3(5)/3(3) = 11182080 poss (16*16*16*15*14*13) | does that look right? Sep 26, 2012 at 15:51
• @baby-rabbit: I can confirm 44,152,809 solutions by brute force enumeration. Also, it can be directly calculated this way: since the average is exactly 4, and the only possibilities are 3, 4, or 5, the possible solution classes are { no 3's or 5's, one 3 and one 5, two 3's and two 5's, ..., nine 3's and nine 5's }. This can be calculated by nCr(18,0)*nCr(18,0) + nCr(18,1)*nCr(17,1) + nCr(18,2)*nCr(16,2) + ... + nCr(18,9)*nCr(9,9) = 44,152,809. This means approximately 11.4% of all possible combinations are valid solutions (44,152,809 / 3^18). Sep 26, 2012 at 22:02
• sum(factorial(18)/factorial(x)/factorial(y)/factorial(z) for x in range(25) for y in range(25) for z in range(25) if 3*x+4*y+5*z == 72 and x+y+z == 18) gives 44152809L Jan 5, 2014 at 7:05

# k (18 17 16 chars)

Back to the original approach, credit to CS for the improvement.

(+/4-){3+18?3}/0


Other approach (17 chars), same method as the J solution, H/T to CS

4+a,-a:9?2 -18?18


Old version:

(72-+/){18?3+!3}/0


Not susceptible to stack-overflow and runs in fixed amount of space.

• What's H/T to CS? Sep 26, 2012 at 14:11
• Sep 26, 2012 at 14:35
• This program helped me discover a bug in my K interpreter- thanks! I didn't previously realize that nilads could be applied to a single argument (which they ignore). Jan 13, 2016 at 16:09

# K, 28

{$[72=+/s:18?3 4 5;s;.z.s]}  ## J, 2018 17 characters (?~18){4+(,-)?9#2  This works in the same way as the previous answer except that the 9 random digits are either 0 or 1 and are negated before being appended. This means there are as many -1s as there are 1s. Adding 4 gives me a list of 3s, 4s and 5s that add up to 72 every time. Previous answer: ({~?~@#)3+(,2-])?9#3  Generates the first 9 holes randomly ?9#3, then copies and inverts them (,2-]) (turns a 3 into a 5 and a 5 into a 3) to generate the final 9. This guarantees that the total will be 72 (since every 3 will have a matching 5 the average total per hole will be 4 and 4x18=72). It then randomly shuffles the result ({~?~@#) to ensure that every combination is possible. • actually you won't generate {3,5,4,4,4...} you are better off shuffling the entire result Sep 25, 2012 at 11:23 • @rachetfreak Good point. I'll edit now. Sep 25, 2012 at 11:31 ## 16-bit x86 machine code under MS-DOS - 45 bytes Hexdump: 0E5F576A12595188ECE44088C3E44130D8240374F400C4AAE2EF595E80FC2475DFAC0432CD29B020CD29E2F5C3  Base64 coded binary: Dl9XahJZUYjs5ECIw+RBMNgkA3T0AMSq4u9ZXoD8JHXfrAQyzSmwIM0p4vXD  Actual source code with some comments:  bits 16 org 0x100 again: push cs ; Save whatever CS we get. pop di ; Use CS:DI as our course buffer.. push di ; Save for later use in the print loop push 18 ; We need 18 holes for our golf course. pop cx ; ch = 0, cl = 18. push cx ; Save for later use. mov ah, ch ; Zero out ah. generate_course: in al, 0x40 ; Port 0x40 is the 8253 PIT Counter 0. mov bl, al ; Save the first "random" value in bl. in al, 0x41 ; Port 0x41 is the 8253 PIT Counter 1. xor al, bl ; Add some more pseudo randomness. and al, 3 ; We only need the two lower bits. jz generate_course ; If zero, re-generate a value, since we need only 3, 4, 5 holes. add ah, al ; Sum in ah register. stosb ; Store in the course buffer. loop generate_course ; Loop for 18 holes. pop cx ; cx = 18. pop si ; si = course buffer. cmp ah, 36 ; 72 holes? jne again ; No, re-generate the whole course. print: ; Yup, we have a nice course. lodsb ; Load the next hole. add al, '2' ; Add ASCII '2' to get '3', '4' or '5' int 0x29 ; Undocumented MS-DOS print function. mov al, ' ' ; Print a space too for better readability. int 0x29 ; Print the character. loop print ; Print the whole course. ret ; Return to the beginning of the PSP where a INT 0x20 happen to be.  Compile with nasm 18h.asm -o 18h.com and run under MS-DOS (or Dosbox), or NTVDM from a 32-bit Windows version. Sample output: 4 5 4 5 4 5 3 4 3 4 3 4 4 5 4 3 5 3  • love assembler... Sep 27, 2012 at 12:18 # Mathematica 71 68 66 60 With 6 chars saved by Tally's suggestion. RandomSample@RandomChoice@IntegerPartitions[72, {18}, {3, 4, 5}]  {5, 4, 3, 3, 5, 3, 5, 5, 3, 3, 4, 5, 3, 5, 4, 4, 5, 3} All possible outcomes are possible, but they are not equally likely. Analysis IntegerPartitions[72, {18}, {3, 4, 5}]  produces all 10 possible partitions (combinations, not permutations) of 72 into 18 elements consisting of 3's, 4's and 5's. RandomChoice selects one of those. RandomSample returns a permutation of that choice. • Hehe, I was just about to post almost the exact same answer, only using RandomChoice instead of RandomInteger. I think you can shave of 4 more characters by doing so. Dec 28, 2014 at 17:25 • Tally, thanks. Your suggestion was helpful. Dec 28, 2014 at 19:56 ## R - 41 x=0;while(sum(x)!=72)x=sample(3:5,18,T);x # [1] 5 3 5 3 3 3 3 3 5 4 5 4 5 4 4 5 5 3  The algorithm is similar to @sgrieve's. • Same problem as @sgrieve above -- nothing prevents it from going over in 18 holes. Sep 25, 2012 at 12:27 • That's not a problem, the sample command in this case always generates 18 values. Sep 25, 2012 at 12:35 ## GolfScript (26 chars) {;0{3rand.3+@@+(}18*])}do  There are some obvious similarities with Ilmari's solution, but also some obvious differences. In particular, I'm exploiting the fact that the average par is 4. • Damn, but that sure is a clever trick with the loop condition there. I came up with {;0{3.rand+.@+}18*])72-}do myself, but couldn't figure out how to get it any shorter from there. +1. Sep 25, 2012 at 23:54 # Python 77 Code from numpy.random import*;l=[] while sum(l)!=72:l=randint(3,6,18) print l  Output [3 4 4 5 3 3 3 5 4 4 5 4 5 3 4 4 5 4]  The import really kills this solution. It uses numpy to generate a 18 numbers between 3 and 5 and keeps generating lists until the sum of the list equals 72. • What prevents the program from reaching 72 well before generating 18 holes? What prevents it from skipping 72? Sep 25, 2012 at 9:35 • The code will always generate 18 holes, then check if the sum equals 72. For example, if the sum after 16 holes was 72, it would still generate another 2 holes, therby pushing the sum above 72 and failing the test. Sep 25, 2012 at 9:40 ## GolfScript, 27 chars {;18{3.rand+}*].{+}*72-}do  Uses the same rejection sampling method as sgrieve's Python solution. Thus, every valid output actually is equally likely. # JavaScript, 6664 61 chars Heavily inspired by TwoScoopsofPig (PHP) and Joe Tuskan (JS). for(a=[s=0];s!=72;)for(s=i=0;i<18;s+=a[i++]=Math.random()*3+3|0);a  for(a=[s=0];s-72;)for(s=i=0;i<18;s+=a[i++]=Math.random()*3+3|0)a  for(a=s=[];s;)for(i=18,s=72;i;s-=a[--i]=Math.random()*3+3|0)a  • s!=72 can be s-72 to save one char. And the last semi-colon ;a isn't needed either for another char. Sep 25, 2012 at 20:21 • i never saw for(i=x;i;i--) before it saves 2 chars from for(i=0;i<x;i++), thanks man! Oct 21, 2013 at 17:37 # Python 2, 70 bytes from random import* print sample(([3,5]*randint(0,9)+[4]*99)[:18],18)  edit: Here's another one, similar to the solution of sgrieve: # Python 2, 73 bytes + equal probability from random import* a=[] while sum(a)-72:a=sample([3,4,5]*18,18) print a  ## Q (25 characters) Original (27) while[72<>sum a:18?3 4 5];a  Sample output 4 4 3 3 4 5 4 3 4 5 5 3 5 5 5 4 3 3  Slightly shorter (25) {72<>sum x}{x:18?3 4 5}/0  Python, 128 120 116 characters import random,itertools random.choice([g for g in itertools.product(*(range(3,6)for l in range(18))) if sum(g)==72])  import statements are still length killers (23 characters only to import 2 function in the namespace) i hope you do not need the result in a near future, as this code first evaluates all possible solutions before chosing one at random. maybe the slowest solution to this problem. i do claim extra kudos for equal probability of each configuration... • import random,itertools Sep 25, 2012 at 20:59 • you are right, that shorten things a bit. Sep 26, 2012 at 9:02 • Other tips: import random as r,itertools as i then use r and i instead of random and itertools. Use 18*[0] instead of range(18), and [3,4,5,6] instead of range(3,6) :) Sep 26, 2012 at 9:20 • i am using python 3: a list comprehension is a generator and has no length, which forbids its use with the choice() function. that's also what makes this code so slow... Sep 26, 2012 at 9:23 • ooops, sorry, i messed up list comprehension and generator expression (i generally avoid list comprehension in favor of generator expression because of the better performance of iterator). so indeed, even in python3 i can still remove some characters... @Alex did it right. Sep 26, 2012 at 15:39 # PHP - 77 Chars <?while(array_sum($a)!=72){for($i=0;18>$i;){$a[++$i]=rand(3,5);}}print_r($a);  Much like sgrieve's solution, this builds a list of 18 holes, checks total par, and either prints it or rejects it and tries again. Oddly enough, our two solutions are the same length. Rather annoyingly, PHP doesn't offer array functions with any brevity of name. Array_sum and print_r are killing me. Suggestions welcome. • Curly braces are not needed here, and sum can be +=. <?while($s!=72)for($s=$i=0;18>$i;$s+=$a[++$i]=rand(3,5));print_r($a); Sep 25, 2012 at 19:13 • That's useful - I never thought to put the logic in the for loop call (and I feel kinda dumb for not incrementing a counter for the sum). Sep 26, 2012 at 19:45 • Thanks – but that isn't actually what I meant by "curly braces not needed"; you could have removed them in the original code too: while(array_sum($a)!=72)for($i=0;18>$i;)$a[++$i]=rand(3,5); Sep 27, 2012 at 16:40
• Well except I run against a stricter php.ini than that because I'm golfing at work; it complains no end about braces being missing/mismatched. Normally I would have. Oct 17, 2012 at 17:53
• That's odd; 5.4.7 with E_ALL|E_STRICT never complains about missing {}'s (since PHP's syntax explicitly allows that). Oct 17, 2012 at 18:21

# Ruby 1.9 (62 chars)

a=Array.new(18){[3,4,5].sample}until(a||[]).inject(:+)==72
p a


# Rails (55 chars)

In the $rails c REPL (in any Rails folder): a=Array.new(18){[3,4,5].sample}until(a||[]).sum==72 p a  Note: It works with Ruby 1.8 if you use shuffle[0] instead of sample. • Do you need whitespace around until? – Kaz Sep 25, 2012 at 19:41 • @Kaz You're right, it's not needed. :) 62 chars now. Sep 26, 2012 at 12:18 • You can use (1..18).map{rand(3)+3} to get the random array ;) Nov 2, 2013 at 18:58 # Lisp (78 69 chars) (do((c()(mapcar(lambda(x)(+ 3(random 3)))(make-list 18))))((=(apply'+ c)72)c)) (do((c()(loop repeat 18 collect(+ 3(random 3)))))((=(apply'+ c)72)c))  It's rather similar to sgrieve's Python solution. Start with c as NIL, check for a sum of 72, the do "increment function" for c generates a list of 18 numbers between 3 and 5, check for 72 again, lather, rinse, repeat. It's refreshing to see do and loop nicely play golf together. # JavaScript, 11699 65 bytes for(i=0,h=[];i<18;)h[i++]=5;while(h.reduce(function(a,b){return a+b})!=72){i=Math.random()*18|0;h[i]=[3,4,4][i%3]}h; h=[0];while(h.reduce(function(a,b){return a+b})-72)for(i=0;i<18;h[i++]=[3,4,5][Math.random()*3|0])h while(i%18||(a=[i=s=0]),s+=a[i++]=Math.random()*3+3|0,s-72|i-18)a  • When I run this in Chrome 21, I get i is not defined. Sep 26, 2012 at 23:24 ## C (123 chars) - effort on efficiency Pipe through wc and it will generate all 44152809 solutions within 10 seconds... char s[19];g(d,t){int i;if(d--){for(i=51,t-=3;i<54;i++,t--)if(t>=3*d&&t<=5*d)s[d]=i,g(d,t);}else puts(s);}main(){g(18,72);}  Oh, well - didn't read the question properly - but given we're generating all solutions then picking a random one with equal probability is a scripting exercise :P # Clojure - 55 (shuffle(mapcat #([[4 4][3 5]%](rand-int 2))(range 9)))  Quite a fun trick.... exploits the mathematical structure of the problem that there must be exactly as many 3 par holes as 5 par holes. # Python 83 import random as r;x=[] while sum(x)!=72:x=[r.randint(3,5) for i in 18*[0]] print x  Like sgrieve's solution, but without numpy Golfing Adrien Plisson's solution: 120->108 characters import random as r,itertools as i r.choice([g for g in i.product(*([3,4,5,6]for l in 18*[0]))if sum(g)==72])  # MATLAB 53 x=[]; while sum(x)~=72 x=3+floor(rand(1,18)*3); end x  Output: x = 4 3 4 4 4 4 5 4 4 3 4 4 3 5 3 5 4 5 • Nice approach, but you can save 4 bytes by typing randi([3,5],1,18) instead of 3+floor(rand(1,18)*3) Jan 14, 2016 at 21:19 # Java (61 chars) while(s!=72)for(i=0,s=0;i<18;i++)s+=3+(int)(Math.random()*3);  Sample output: 5 4 3 4 5 3 4 4 3 5 4 4 4 4 3 4 4 5  • I'm no Java expert, but shouldn't there be a declaration of s and i, and some kind of call to System#println(..)? Aug 26, 2015 at 8:17 • This is just a code snippet, not a program. And it actually looks very much like @JoeIbanez' C version. Nov 4, 2015 at 22:22 # C (94 chars) int h[18],s=0,i; while(s!=72)for(i=s=0;i<18;s+=h[i++]=rand()%3+3); while(i)printf("%d ",h[--i]);  The s=0 on line 1 may not be required, because what are the chances an uninitialized int will equal 72? I just don't like reading uninitialized values in straight C. Also, this probably requires seeding the rand() function. ## output 3 3 3 4 5 5 3 3 4 5 5 4 3 4 5 5 5 3  • So basically you're gonna loop through random strings of 18 numbers ranged 3 to 5 until one happens to equal 72? Good thing efficiency isn't a requisite. Sep 25, 2012 at 23:10 • @KeithS To be fair, that's what the majority of the answers to this question are doing. Sep 25, 2012 at 23:19 ## Bash shell script (65 chars) shuf -e for x in {0..8} do echo$((r=RANDOM%3+3)) $((8-r)) done  (shuf comes from the GNU coreutils package. Also, thanks Gareth.) # C# (143 non-whitespace): ()=>{ var n=new Math.Random().Next(10); Enumerable.Range(1,18) .Select((x,i)=>i<n?3:i>=18-n?5:4) .OrderBy(x=>Guid.NewGuid()) .ForEach(Console.Write); }  • new Guid() creates an empty GUID. To actually generate a unique GUID you need to call a static method Guid.NewGuid. Sep 26, 2012 at 5:18 • And you have two off-by-one errors (so to speak): the comparisons should be i<n and i>=18-n, not the other way around. And you could reduce the size by using a constant 3 instead of x-1 and 5 instead of x+1. And then you could replace Enumerable.Repeat by Enumerable.Range. Sep 26, 2012 at 14:20 • Edited; still 143 chars Sep 26, 2012 at 16:16 • There is no Math.Random, it's System.Random. Nov 7, 2013 at 9:15 • Another C# approach (143 chars): var r=new Random();for(;;){var e=Enumerable.Range(1,18).Select(i=>r.Next(3,6)).ToList();if(e.Sum()==72){e.ForEach(i=>Console.Write(i));break;}} Jan 6, 2014 at 3:40 # Haskell, 104102 98 chars. import System.Random q l|sum l==72=print l|1>0=main main=mapM(\_->randomRIO(3::Int,5))[1..18]>>=q  • [1..n]>>[r] is slightly shorter than replicate n$r. Sep 27, 2012 at 19:17
• Also changed sequence to mapM. Sep 27, 2012 at 23:14

## Perl, 74

{@c=map{3+int rand 3}(0)x18;$s=0;$s+=$_ for@c;redo unless$s==72}print"@c"


Alternative solution:

@q=((3,5)x($a=int rand 9),(4,4)x(9-$a));%t=map{(rand,\$_)}(0..17);print"@q[@t{sort keys%t}]"


# TXR (99 chars)

@(bind g@(for((x(gen t(+ 3(rand 3))))y)(t)((pop x))(set y[x 0..18])(if(= [apply + y]72)(return y))))


This expression generates an infinite lazy list of random numbers from 3 to 5:

(gen t (+ 3(rand 3)))  ;; t means true: while t is true, generate.


The rest of the logic is a simple loop which checks whether the first 18 elements of this list add up to 72. If not, it pops an element off and tries again. The for loop contains an implicit block called nil and so (return ...) can be used to terminate the loop and return value.

Note that the 99 character length includes a terminating newline, which is required.

• I put in a commit that allows the (t) to be replaced by (). :)
– Kaz
Sep 25, 2012 at 20:03

## APL 12

4+{⍵,-⍵}?9⍴2


Note that I have the index origin set to 0, meaning arrays start at 0. You can set this with ⎕IO←0.

• The question asks a program that can produce every possible configuration. Yours can produce simmetric ones. You can't produce for example 555455555333333343, at least it seems so to me. Dec 27, 2014 at 19:11

# R, 42 bytes

a=0;while(sum(a)-72)a=sample(3:5,18,r=T);a


sample, by default, draws evenly among the possible values (here 3 4 5). r=T stands for replace=TRUE and allows sample with replacement.

## CJam, 17 14 bytes

CJam is newer than this challenge, but this is not the shortest answer anyway, so that doesn't really matter.

Z5]Amr*I4e]mrp


Test it here.

To maintain the total of 72, each 3 must be paired with 5. So here is how it works:

Z5]            e# Push [3 5].
Amr         e# Get a random number between 0 and 9.
*        e# Repeat the [3 5] array that many times.
I4e]    e# Pad the array to size 18 with 4s.
mr  e# Shuffle the array.
p e# Print it.
`