Simulate reproduction in a population of oozes

Question

Reproductive strategy of oozes can be summarized as follows:

o O 8 oo

A population of oozes at generation N is described by a string, for example:

ooooo88ooOoOo8Ooooo8OOoo8Oo8Oo8oo8oooooo8OOooO88o

To compute the population at generation N+1, take one character randomly, and replace it by the result of ooze evolution:

• If o, replace by O
• If O, replace by 8
• If 8, replace by oo

Generation 0 is the one-character string o. Your program or function should get a positive number N, and output the population of oozes at generation N. At each generation, each ooze should have the same chance (to within 1% accuracy) to evolve.

Test cases (actual results may vary due to randomness):

1 -> O
2 -> 8
3 -> oo
4 -> Oo
5 -> OO
10 -> OO8
20 -> oo8oooo
30 -> oOoooOO8O
100 -> 8o8oO8OOooOo8OOoo88oOO8OOO
200 -> 88OOo8oooo8OOoooOoOOO8O8OO88o8Oo8oooOooooooOo8OooO888
1000 -> 8Ooooo88OO8o8O8oooOOoOOO88oOoO88OOoO8OOOooOOo8OO88O8OO8OO8ooo8oOO8OoooO88OooooooooOo8oooOO8OO8Oo8Oooo8O88oooOooO8Oo8ooOOOOo8OooOo8OoooooooO8oOooooOooOO8oOO8ooo8Ooooo8ooo8ooOOooO8OOoO8oO8oo88ooo8oO8OO8o888oO8OOoO8o8ooO8O88OOOoO8oooO8OoOoOo88O88oo88ooo8oO8o8oOooOo

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If your solution has running time of O(n), please specify it explicitly!

Answer 1

Python 3, 114 bytes

from random import*
def f(n,s=b'o'):k=randrange(len(s));return n and f(n-1,s[:k]+b'oO8o'[-~s[k]%3::3]+s[k+1:])or s

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Interesting observation: the ascii values of oO8 are 111, 79, and 56, respectively. If you take these modulo 3, you get 0, 1 and 2.

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Additional observation: you can validate the generation of your final string by substituting 'o' with 3, 'O' with 4 and '8' with 5; then taking the sum of your list and subtracting 3 from the total.

This works for all strings regardless of random variations, because each replacement in your string increases this sum by 1:

'o' (3) -> 'O'  (4)
'O' (4) -> '8'  (5)
'8' (5) -> 'oo' (3+3 = 6)

We then just need to correct for the offset of 3.

Validate it online!

Answer 2

Ruby, 79 77 73 72 61 bytes

->n,s=?o{n.times{s[w=rand(s.size)]=%w[O 8 oo][s[w].ord%3]};s}

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-11 bytes thanks to Value Ink and Jitse

Answer 3

APL (Dyalog Unicode), 40 32 31 bytes^SBCS

Full program. Prompts for N from stdin.

'o8O'[{∊⌷∘3(1 1)2@(?≢⍵)⊢⍵}⍣⎕,1]

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'o8O'[…] select the following characters from the string "oO8":

 ,1 the list [1]

 ⎕ prompt for N from stdin

 {…}⍣ apply the following anonymous lambda to [1], that N times:

  ⊢⍵ on the argument…

  @(…) at position…

   ≢⍵ the length of the argument

   ? random index in that range

  … apply the following tacit function:

  ⌷∘3(1 1)2 use the number to select from the list [3,[1 1],2]:

  ∊ ϵnlist (flatten)

Answer 4

Pyth, 25 bytes

uXGJOlG@c"O 8 oo")C@GJQ\o

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Written by @FryAmTheEggman, similar idea to my earlier post but much cleaner as it reduces instead of looping.

How it works

uXGJOlG@c"O 8 oo")C@GJQ\o
u                     Q\o - Reduce 'o' Q=input times
   JOlG                   - With random number J in the range [0,length G), 
                            where G is the previous list
 XG                       - Replace the element in G at index J...
       @c"O 8 oo")        - With an element of "O 8 oo" split by 
                            whitespace, at index...
                  C@GJ    - ...of the codepoint of the element in G at index J

Pyth, 38 bytes

K\oJ["oo"\o\O\8)VQ=kOlK=KXKk@JhxJ@Kk;K

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My original solution, less sophisticated.

How it works

K\oJ["oo"\o\O\8)VQ=kOlK=KXKk@JhxJ@Kk;K
K\o                                    - K = 'o', start
   J["oo"\o\O\8)                       - J = ['oo', 'o', 'O', '8']
                VQ                     - Loop Q=input times
                  =kOlK                - k = random number from 0..length of K
                       =K              - K equals...
                         XKk           - K with the element at index k replaced by...
                            @Jh        - The item in J at index+1 of...
                               xJ      - The index (in J) of...
                                 @Kk   - The element of K at index k
                                    ;K - End loop, print K     

Answer 5

05AB1E, 26 bytes

'osFÐg<ÝΩ©è…oO8S„O8„ooª‡®ǝ

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Answer 6

R, 109 97 93 bytes

for(i in 1:scan())T=append(T,switch(T[j],"O",O=8,"8"=c("o","o")),j<-sample(sum(T>0),1))[-j];T

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Output as an array.

Thanks to Robin Ryder for golfing out 6 bytes, for pointing out a bug in a previous version, and for golfing out an additional 4 bytes.

Answer 7

J, 54 bytes

'oO8'{~(((1+2={)`[`(1"0@])}#(3|1+{)`[`]})~1?#)^:(]`0:)

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Wholly different approach to shave off 2 bytes

original solution

J, 56 bytes

'oO8'{~(({.,(i.@3(>:@i.{ ::0 0[){),>:@[}.])~1?#)^:(]`0:)

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Had an equal byte solution, but adjusted it slightly using Adam's idea of doing all the calculation in pure integers, and saving the translation-to-string step till last, which I felt looked a bit cleaner.

Answer 8

Perl 6, 55 bytes

{('o',{S:p(rand*.comb)[.]=<O 8 oo>[$/.ord%3]}...*)[$_]}

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Explanation

{                                                     }  # Anonymous block
     ,                                       ...*  # Infinite sequence
  'o'  # Start with string "o"
      {                                     }  # Compute next item by
       S  # replacing
        :p(rand*.comb)  # starting at random position
                      [.]  # any character
                         =<O 8 oo>  # with "O", "8" or "oo"
                                  [$/.ord%3]  # depending on ASCII code mod 3
 (                                               )[$_]  # nth item of sequence

Answer 9

C# (Visual C# Interactive Compiler), 172 158 150 149 144 137 130 128 bytes

a=>{dynamic r=new Random(),g="o",i;while(a-->0)g=g.Remove(i=r.Next(g.Length),1).Insert(i,"O,8,oo".Split(',')[g[i]%3]);return g;}

Try it online!

-14 bytes thanks to @Jitse's observation about character modulus

-8 bytes by renaming a variable I forgot about

-1 byte by switching to a while loop

-5 bytes by not saving the current character to a variable

-7 bytes by switching to the interactive compiler

-7 bytes by chaining declarations and inlining assignment thanks to @my pronoun is monicareinstate

-2 bytes by changing to string split over character comparison thanks to @Olivier Grégoire for inspiration

Answer 10

Perl 5, 79 bytes

sub f{$_[0]?do{$_=f(-1+pop);substr($_,rand length,1)=~y/oO8/O82/;s,2,oo,r}:"o"}

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sub f {
  $_[0]
  ? do{
      $_ = f(-1+pop);
      substr($_,rand length,1) =~ y/oO8/O82/;
      s,2,oo,r
    }
  : "o"
}

srand(7) and print "$_ -> ",f($_),"\n" for 1..40

Answer 11

Charcoal, 38 bytes

⊞υoＦＮ«≡⊟υo⊞υO¦O⊞υ8Ｆ²⊞υo≔‽ＬυιＵＭυ§υ⁺λι»υ

Try it online! Link is to verbose version of code. Outputs an array, which is like a string but vertical (+1 byte to output the array horizontally). Explanation:

⊞υo

Start with a single o.

ＦＮ«

Loop the given number of generations.

≡⊟υ

Remove the last character and switch on it.

o⊞υO

If it's an o then push an O.

O⊞υ8

If it's an O then push an 8.

Ｆ²⊞υo

Otherwise push o twice.

≔‽ＬυιＵＭυ§υ⁺λι

Rotate the array by a random amount. This causes the oozes to be evolved in a random order.

»υ

Finally output the resulting array.

Answer 12

Japt, 32 31 29 bytes

_gZÊö _Ä %3ª1ö2Ãc}g[]á)Ëg"oO8

Try it

 _               // function taking array
  gZÊö           // replace a random element with :
       _Ä %3     // element incremented mod 3
      ª1ö2Ã      // or [0,0]
            c}   // flattens

g[]á)            // run the function input times with initial value of array, return last element
      Ëg"oO8     // convert values to o O 8

Thanks to @Embodiment of Ignorance for reminding me I don't need = at beginning

Answer 13

Python 2, 104 bytes

from random import*
l=['o']
exec"i=randrange(len(l));l[i:i+1]='oO8o'[-~ord(l[i])%3::3];"*input()
print l

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Golfing Jitse's solution using the mutability of lists.

Answer 14

Java (JDK), 138 bytes

n->{var s=new StringBuffer("o");for(int i;n-->0;s.replace(i*=Math.random(),i+1,"O,8,oo".split(",")[s.charAt(i)%3]))i=s.length();return s;}

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Credits

• -2 bytes thanks to Kevin Cruijssen

Answer 15

Zsh, 75 73 bytes

s=o
m=(oo 8 O)
repeat $1 ((n=1+RANDOM%$#s))&&s[n]=$m[m[(i)$s[n]]-1]
<<<$s

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I want to focus here specifically:

$m[m[(i)$s[n]]-1]
   m[        ]     # from array $m:
     (i)           #   get the index of 
        $s[n]      #   the nth character in the string (as a pattern)
                   #   if not found substitute 4 (length of array + 1)
              -1   # subtract one
$m[             ]  # substitute the element at that index

Answer 16

JavaScript (ES10), 91 bytes

Similar to the ES6 version, but returns an array of characters.

n=>(g=P=>n--?g(P.flatMap(c=>i--?c:'8O'[c|c>g]||['o','o'],i=Math.random()*P.length|0)):P)`o`

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JavaScript (ES6),  98 ... 94  93 bytes

n=>(g=P=>n--?g(P.replace(/./g,c=>i--?c:'8O'[c|c>g]||'oo',i=Math.random()*P.length|0)):P)('o')

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Commented

n => (                       // n = number of generations
  g = P =>                   // g is a recursive function taking the population string P
    n-- ?                    // decrement n; if it was not equal to 0:
      g(                     //   do a recursive call:
        P.replace(/./g, c => //     for each character c in P:
          i-- ?              //       if we haven't reached the requested position:
            c                //         leave c unchanged
          :                  //       else:
            '8O'[            //         replace with:
              c | c > g      //           'O' is c != 8 and c is lowercase
            ]                //           '8' is c != 8 and c is uppercase
            || 'oo',         //           'oo' if c = 8
          i = Math.random()  //       compute a random position i within the current
              * P.length | 0 //       population string
        )                    //     end of replace()
      )                      //   end of recursive call
    :                        // else:
      P                      //   return the final population
)('o')                       // initial call to g with P = 'o'

Answer 17

Python 3.8, 91 bytes

f=lambda n,s='o':n and f(n-1,s[:(k:=id(s)//7%len(s))]+'oO8o'[-~ord(s[k])%3::3]+s[k+1:])or s

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I'll be perfectly honest, I don't know for sure that this is valid randomness. It seems like it to me, but I'm not sure how I'd determine one way or the other - if someone could confirm or deny, that'd be much appreciated.

Assuming validity, this is a modification of Jitse's answer that gets rid of the import. id(s) gives a different integer every time, but just taking it modulo len(s) gave results that were too consistent. Integer dividing the id by 7 seemed to do the trick, but again, I'm not sure how to verify.

If this turns out not to be valid, I'll delete immediately.

Answer 18

Jelly, 21 17 bytes

1F‘JX$¦ḃ3Ʋ¡ị“oO8”

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A full program that takes n as its argument and implicitly outputs the state of the oozes after that many generations.

Explanation

1                 | Literal 1
         Ʋ¡       | Repeat the following the number of times given by the argument
 F                | - Flatten
  ‘  $¦           | - Increment the item at the index given by:
   J              |   - Sequence along the list
    X             |   - Random number fron the sequence
       ḃ3         | Convert to bijective base 3
           ị“oO8” | Index into "oO8"

Answer 19

Red, 93 bytes

func[n][s: copy"o"loop n[replace at s i: random length? s s/:i select[#"o"#"O"#"8":oo]s/:i]s]

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Answer 20

K (oK), 51 bytes

{"oO8"x{{,/(x#t),((1;2;0 0)t@x),(x+1)_t}1?#t:x}/,0}

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No doubt this can be done much shorter / more elegant (using ammend?). I'm somewhat happy that it works at least.

Answer 21

Retina, 29 27 bytes

K`o
"$+"{@T`\oo`\O80`.
0
oo

Try it online! Edit: Saved 2 bytes when I realised how I could combine @ with T. Explanation:

K`o

Replace the input with the initial generation.

"$+"{

Repeat the remaining stages for the given number of generations.

@T`\oo`\O80`.

The O is a metacharacter and needs to be escaped. The o is also a metacharacter, so the first o is literal, while the second o represents O80 from the destination pattern. This therefore transliterates the characters oO8 to O80. The final . means that each character is treated as a separate match for the purposes of the @ operator, which chooses one match (i.e. character) at random to be transliterated.

0
oo

Fix up any 0 to oo. (This stage does not need to be conditional.)

Answer 22

Python 3, 142 bytes

from random import*
def f(i,x='o'):i-=1;s=randint(0,len(x)-1);o={'o':'O','O':'8','8':'oo'};x=x[:s]+o[x[s]]+x[s+1:];return x if i<1else f(i,x)

Answer 23

Icon, 85 bytes

procedure f(n)
s:="o"
1to n&s[p:=?*s]:=["O",8,"oo"][find(s[p],"oO8")]&\z
return s
end

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Answer 24

C (gcc), 101 bytes 104 117 bytes

char*h,g[9999];l;f(a){*g='o';for(l=1;a--;(*h="O8o"[*h%3])-'o'?:bcopy(h,h+1,l++))h=g+rand()%l;g[l]=0;}

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(Many thanks to ceilingcat for the awesome code golfing help and ideas!)

Ok, except for large generation count buffer overflow and the fact that I seeded random outside the code, this now works. Making g bigger could put the overflow size above what an int can hold if needed.

Commented

char *h,g[9999]         // Work pointer and a fixed size buffer.  
l;                      // int length of string (number of slimes)
f(a){                   // a is generation
  *g='o'                // Set first value. 
  for(l=1;              // Length is 1.
   a--;                 // consume a generation
   (*h="O8o"[*h%3])     // Use the mod 3 trick to index into the next symbol and assign the new slime character.
   -'o'?:               // if we went back to 'o', grow the string
   bcopy(h,h+1,l++))    // move all the values up in in array to length (including new 'o' symbol) Note: bcopy() can overlap src and dest.
    h=g+rand()%l;       // for each loop, find which slime to evolve and point h to it.
  g[l]=0;}              // NUL Terminate the g buffer to make it a string. 

Answer 25

Lua, 106 101 110 bytes

Changed Code to function format + 9 bytes

e={"O",8,"oo"}for i=1,t do s=math.random(1,#o)o=o:sub(1,s-1)..e[o:sub(s,s):byte()%3+1]..o:sub(s+1)end return o

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Answer 26

C (gcc) (with -m32 compiler flag), 174 172 bytes

Thanks to ceilingcat for the suggestions.

Not competing (there are already shorter versions in C), but this uses a different method.

Instead of using a hard-coded output buffer, I use a linked list on the stack to hold each cell's state and traverse the list to locate cells to mutate. If the cell splits in two, the function calls itself to hold the new cell state and adds itself into the list chain. As the list is not necessarily linear on the stack, the last function prints the list of cells (intermediate callers set their list start to NULL after control returns to them to prevent unwanted output.)

g(i,j,s,p)int*s,*p;{int a[2]={},r;for(j++?*a=*p,*p=a:(s=a);i--;++p[1]>2?p[1]=0,g(i,j,s,a),s=i=0:0)for(r=rand(p=s)%j;r--;p=*p);for(;s;s=*s)printf(L"oO8"+s[1]);}f(i){g(i,0);}

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Answer 27

APL(NARS), chars 62, bytes 124

{⍵{⍺=0:⍵⋄(⍺-1)∇(⍵↑⍨k-1),(('oO'⍸k⊃⍵)⊃"O"'8'"oo"),⍵↓⍨k←?≢⍵},'o'}

test:

  h←{⍵{⍺=0:⍵⋄(⍺-1)∇(⍵↑⍨k-1),(('oO'⍸k⊃⍵)⊃"O"'8'"oo"),⍵↓⍨k←?≢⍵},'o'}
  h 0
o
  h 4
oO
  h 10
8OO
  h 100
8oOOO8ooOO8oOOoO8oOooooO8OO
  h 200
8OO888Ooo8OO8oO88O8oo8oooooOo8ooO8OooOO88OoO8O8o8Oo

but it has problems if the argument is >500, the 73 chars code below has not these problems:

r←f w;k
r←,'o'
→0×⍳0>w-←1⋄r←(r↑⍨k-1),(('oO'⍸k⊃r)⊃"O"'8'"oo"),r↓⍨k←?≢r⋄→2

  f 1000
    O8oooo8OoooO8ooOO88oo88OOOoo8oOoO8888oo88ooOOOoooooo8oooOO8OooO8O8oOO8oOOOo88Oo
  Ooooo88O8o8ooooo8OOooOO8O8OOOoo8OoO8Oo88ooOOoooO888O8o8OoOOoooOo8oooo8OoO
  88Oooo8O8OoooooooOo88oo8oooooo8OOoO8oOO8Oo8oo8oO88oo8OOoOoOOoOoOoo8O88o8O
  88OoO8OOoOo8Oo8ooo8OoooooooooOOooO8oo88