Code Golf: Your own pet ASCII snake

Question

So, I wrote myself a one-liner which printed out a snake on the console. It's a bit of fun, and I wondered how I might condense my code...

Here's a (short) example output:

                +
                 +
                  +
                   +
                   +
                   +
                  +
                   +
                    +
                    +
                    +
                     +
                     +
                      +
                      +
                       +
                      +
                     +
                     +
                    +

Here's the specs:

• In each line, a single non-whitespace character (whichever you like) is printed to the console, initially with 29 to 31 spaces padding to the left of it.
• Each iteration, a random decision is made between these three actions
  • The amount of padding decreases by 1
  • The amount of padding remains the same
  • The amount of padding increases by 1

Do this 30 times, to print 30-segment long a snake to the console.

The shortest answer in bytes wins.

Answer 1

05AB1E, 15 14 bytes

30DF2Ý<+ΩD0sú,

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Uses 0.

Explanation

30DF2Ý<+ΩD0sú,
30D            # Push 30 to the stack (One for the amount of iterations we are going to perform and one for the initial padding)
   F           # Pop one of the 30s and perform the following that many times...
    2Ý          # Push [0,1,2] ...
      <         # and create [-1,0,1] from that
       +        # Add the last padding to every entry (e.g. 30 in the beginning resulting in [29,30,31]
        Ω       # Pick one of the results at random ...
         D      # and push it to the stack twice
          0     # Push 0 (Any character will work fine here) ...
           sú   # and pad it with the randomly chosen amount of spaces in the front
             ,  # Finally print the result with a trailing newline

Answer 2

Random Brainfuck, 123 122 121 bytes

+[--[<]>>+<-]>+[->+>+>+<<<]++++++++++>>++<[>>[->+<<.>]>[-<+>]>?>+++<[>->+<[>]>[<+>-]<<[<]>-]>-->,<[-<<<+>>>]<<<<+.-<<.>-]

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Random Brainfuck is an extension of brainfuck, with the helpful addition of the ? command, which sets the current cell to a random byte. This prints a snake made of !s, which looks more like footsteps than a snake funnily enough.

How It Works:

+[--[<]>>+<-]>+ Create the value 30
[->+>+>+<<<]    Copy it three times
++++++++++      Create a newline cell
>>++<            Adds 2 to the second copy to make it a space and move to the counter
[ While counter
  >>[->+<<.>]>[-<+>] Print out the padding cell number of spaces
  ?>+++<[>->+<[>]>[<+>-]<<[<]>-] Get 3-(random byte%3)
  >-->,<[-<<<+>>>]   Add (result-2) to the padding cell
  <<<<+.-<           Print an exclamation mark
  <<.                Print a newline
  >-                 Decrement counter
] end loop

Another solution that sticks to the letter of the question, rather than the spirit.

87 bytes

+[--[<]>>+<-]>+[->+>+>+<<<]++++++++++>++>[>[->+<<<.>>]>[-<+>]?[,<+>]?[,<->]<<<+.-<.>>-]

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This one is heavily biased towards leaving the padding alone, but increasing or decreasing the padding are both equally possible. Each one has a slightly less than 1 in 256 chance to happen.

Answer 3

C (gcc), 61 58 56 bytes

Answer edited to reflect rules changes...

i;f(s){for(s=i=31;--i;printf("%*d\n",s+=1-rand()%3,8));}

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Answer 4

C# (.NET Core), 112 110 106 100 99 98 bytes

v=>{var r="";for(int t=30,i=t;i-->0;r+="+\n".PadLeft(t+=new System.Random().Next(3)-1));return r;}

-1 byte thanks to @raznagul.
-1 byte thanks to @auhmaan.

Explanation:

Try it online.

v=>{                      // Method with empty unused parameter and no return-type
  var r="";               //  Result-string, starting empty
  for(int t=30,           //  Temp-integer, starting at 30
      i=t;i-->0;          //  Loop 30 times
    r+=                   //   Append the result-String with:
       "+\n"              //    The character and a new-line,
            .PadLeft(     //    left-padded with `t` spaces,
                     t+=new System.Random().Next(3)-1));
                          //    after `t` first has been changed with -1, 0, or 1 randomly
  return r;}              //  Return the result-string

Answer 5

Retina, 24 bytes

30* +
-29{¶<`^
 
S,2@1`

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Explanation

30* +

Initialise the working string to the first line, i.e. 30 spaces and a +.

-29{¶<`^
 

There's a space on the second line. -29{ wraps the remainder of the program in a loop, which is run 29 times. ¶< prints the working string at the beginning of each loop iteration with a trailing linefeed. The atomic stage itself inserts a space at the beginning of the string (the basic idea is to insert one space, and then randomly remove 0–2 spaces, because that's a byte shorter than randomly choosing between deletion, inserting and no-op).

S,2@1`

This matches the empty regex against the input, which gives us every position between characters (and the start and end of the string). Then ,2 keeps only the first three matches, i.e. the matches after zero, one and two spaces. @ selects a random one of those three matches. Then the split stage (S) splits the input around that match. And the 1 tells it to keep only the second part of the split. In other words, we discard everything up to our random match.

The 30th line, which is the result of the final loop iteration, is printed implicitly at the end of the program.

Answer 6

VBA, 60 59 49 Bytes

For l=1To 30:?Spc(30+i)"+":i=i+Sgn(Rnd()-.5):Next

Paste it in the Immediate window and hit enter. (Make sure explicit declaration is turned off!)

Far more likely to move than to stay in a line (i.e. actions are not equally weighted) but that was not a specified requirement (Fortunately!)

{EDIT} Saved 1 byte by removing the space between =1 and To

{EDIT2} Saved 10 bytes thanks to remoel's comment

Old Versions:

'V1
i=30:For l=1 To 30:?String(i," ")&"+":i=i+Sgn(Rnd()-.5):Next
'V2
i=30:For l=1To 30:?String(i," ")&"+":i=i+Sgn(Rnd()-.5):Next

Answer 7

C, 56 bytes

n;f(p){n>29?n=0:f(printf("%*d\n",n++?p-rand()%3:31,0));}

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Explanation:

n; // As a global variable, n is initialized to zero.
f(p)
{
    // Call the function recursively until n > 29.
    n > 29

        // At the end, set n back to zero.
        ? n=0

        // On the first iteration, n == 0 and p has an indeterminate value.
        // 'n++ ? p-rand()%3 : 31' returns 31 (without reading p), and thus
        // 30 spaces get printed. printf() returns the number of characters
        // printed, 32 (30 spaces + '0' + '\n').
        //    On subsequent iterations, p has the value the previous printf
        // call returned, which is the padding on last iteration + 2. Also,
        // n > 0, so the same expression now returns p-rand()%3, and thus
        // the padding changes either by -1, 0, or 1 spaces. The function
        // is again called with the value of the current line's padding + 2.
        : f(printf("%*d\n", n++ ? p-rand()%3 : 31, 0));
}

C (gcc), 55 bytes

n;f(p){n=n<30&&f(printf("%*d\n",n++?p-rand()%3:31,0));}

Depends on f "returning" the value assigned to n in the function, which is undefined behaviour, but works consistently with gcc when no optimizations are enabled.

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Answer 8

APL (Dyalog), 20 bytes

1 byte saved thanks to ngn

↑'+'↑⍨¨-+\30,2-?29⍴3

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Answer 9

JavaScript (ES8), 63 62 60 bytes

Includes a trailing newline. *2-1 could be replaced with -.5 for a 1 byte saving but the chances of each line being the same length as the previous line would be greatly increased. Of course, as "random" isn't defined in the challenge, the RNG could be replaced with new Date%3-1 for a total byte count of 55.

f=(x=y=30)=>x?``.padEnd(y+=Math.random()*2-1)+`+
`+f(--x):``

Saved a byte thanks to someone who deleted their comment before I could catch the name. I'd actually tried it this way with repeat and padStart but didn't think to try padEnd - don't know why!

o.innerText=(
f=(x=y=30)=>x?``.padEnd(y+=Math.random()*2-1)+`+
`+f(--x):``
)()

<pre id=o>

---

Bonus

For the same number of bytes, here's a version that takes the number of starting spaces & iterations as input.

f=(x,y=x)=>x?``.padEnd(y)+`+
`+f(--x,y+Math.random()*2-1):``

o.innerText=(
f=(x,y=x)=>x?``.padEnd(y)+`+
`+f(--x,y+Math.random()*2-1):``
)(i.value=30);oninput=_=>o.innerText=f(+i.value)

<input id=i type=number><pre id=o>

Answer 10

Python 2 , 83 65 64 bytes

Straightforward approach:

import os
k=30
exec"print' '*k+'+';k+=ord(os.urandom(1))%3-1;"*k

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Thanks to @Rod for saving some bytes! Thanks to @ovs for -1 byte!

Edit: changed variable name and output string to the letter 's'

More snake-like output for 88 bytes:

from random import*
s=[30,0]
exec"print' '*sum(s)+'(S)'[s[-1]+1];s+=[randint(-1,1)];"*30

Answer 11

Java 8, 89 87 bytes

First golf, I'm sure it could be much better..

Edit: Fixed first line thanks to Steadybox.

l->{for(int a=31,b=a;--a>0;){System.out.printf("%"+b+"c\n",'+');b+=2-Math.random()*3;}}

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 l->{                                           //Begin lambda
    for(int a=31,b=a;--a>0;)                  //Initialise vars, loop through 30 lines
    {
        System.out.printf("%"+b+"c\n",'+');     //Print result
        b+=2-Math.random()*3;                   //Change padding by -1, 0, or 1
    }

Answer 12

Java 8, 131 129 127 126 119 108 101 bytes

v->{String r="";for(int i=30,j,t=i;i-->0;r+="+\n")for(j=t+=Math.random()*3-1;j-->0;r+=" ");return r;}

Explanation:

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v->{                     // Method with empty unused parameter and String return-type
  String r="";           //  Result-String, starting empty
  for(int i=30,j,t=i;    //  Two index integers, and a temp integer (starting at 30)
      i-->0;             //  Loop 30 times:
      r+="+\n")          //    After every iteration: Append the character and a new-line
    for(j=t+=Math.random()*3-1;
                         //   Change `t` with -1, 0, or 1 randomly
        j-->0;r+=" ");   //    And append that many spaces to the result-String
  return r;}             //  Return the result-String

Old 119 byte answer:

v->{String s="",r=s;int i=90,t=30;for(;i-->t;s+=" ");for(;i-->0;t+=Math.random()*3-1)r+=s.substring(t)+"+\n";return r;}

Explanation:

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v->{                      // Method with empty unused parameter and String return-type
  String s="",            //  Temp-String, starting empty
         r=s;             //  Result-String, starting empty
  int i=90,t=30;          //  Temp integer, starting at 30
  for(;i-->t;s+=" ");     //  Fill the temp String with 60 spaces
  for(;i-->0;             //  Loop 30 times:
      t+=Math.random()*3-1//    After every iteration: Change `t` with -1, 0, or 1 randomly
    r+=s.substring(t)     //   Append the result with `60-t` amount of spaces
       +"+\n";            //   + the character and a new-line
  return r;}              //  Return the result-String

Answer 13

PHP, 61 bytes

for($p=32;$i<30;$i++)echo str_pad("+
",$p+=rand(-1,1),' ',0);

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Answer 14

Charcoal, 14 bytes

× ³⁰Ｆ³⁰«↙+Ｍ‽³→

Try it online! Link is to verbose version of code. Explanation:

× ³⁰            Print 30 spaces (forces the desired indentation)
    Ｆ³⁰«        Repeat 30 times
        ↙+      Print a `+` and move down and left one square
          Ｍ‽³→  Move right a random number of squares from 0 to 2

Would be only 10 bytes if there was no initial indentation requirement.

Answer 15

R, 72 69 67 bytes

cat(sprintf(paste0("% ",cumsum(c(30,sample(3,29,T)-2)),"s"),"+\n"))

Thanks to Zahiro Mor for 2 extra bytes!

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Answer 16

Perl, 36 bytes

perl -E '$#a=29;map{$#a+=rand(3)-say"@a -"}@a'

Answer 17

Japt, 13 bytes

Returns an array of lines.

30ÆQù1nH±1n3ö

Test it

---

Explanation

30Æ               :Create the range [0,30) and pass each through a function
   Q              :  The " character
    ù             :  Pad start to length...
           3ö     :    Random element from the range [0,3)
         1n       :    Subtract 1
       H±         :    Add the result of that to H (inititally 32)
     1n           :    Subtract 1 to avoid the possibility of the first line being 33 characters long in total

---

Bonus

For 2 bytes less, here's a version that takes the number of starting spaces & iterations as input.

U°ÆQùU±1n3ö

Try it

---

Alternative RNGs

The last 4 bytes can be replaced with any of the following:

MrJ1     :A random float between -1 and 1
Jõ ö     :Generate the range [-1,1] and return a random element
3ö É     :An alternative way of writing the method used above
½nMr     :0.5 subtracted from a random float between 0 and 1

Answer 18

Ruby, 45 39 bytes

x=30
x.times{puts' '*(x+=rand(3)-1)+?S}

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Modifying x during the loop does not affect the loop counter. I chose S as a particularly snakelike output character.

-6 bytes: Use rand(3)-1 instead of [-1,0,1].sample. Thanks, Eric Duminil!

Answer 19

Swift, 101 bytes

import UIKit
var g=29;for _ in 0...g{print((0..<g).map{_ in" "}.joined(),0);g+=Int(arc4random()%3)-1}

Explanation

A full program. This uses a rather odd trick: arc4random() is a member of the Darwin module, but UIKit also comes with this function installed, so it saves a byte :) Also uses one of my Swift golfing tips for repeating strings an arbitrary number of times.

import UIKit        // Imports the UIKit module, necessary for the RNG.
var g=29;           // Declares an integer variable g by assigning it to 30.
for _ in 0 ... g {  // Execute the code block 30 times (for each integer in [0; g]):
 print(             // Output the following:
  (0..<g).map       // For each integer in [0; g)...
   {_ in" "}        // ... return a literal space character. 
    .joined()       // ... And join the result to a single string.
             ,0     // Also print a "0" preceded by a single space (g starts from 29).
 );
g+=                 // Increment the variable g by...
   arc4random()%3   // ... A random integer, modulo 3...
   Int(...)-1       // ... Casted to an integer (yes, this is needed!) and decremented.
}

Answer 20

R, 54 53 bytes

cat(sprintf('
%*s',cumsum(c(30,sample(3,29,T)-2)),0))

Similar idea as above, but with shortened sprintf code and a shorter character string literal. Instead of \n (two bytes) I’m using a literal line break (one byte).

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Answer 21

SenseTalk, 237 198 Bytes

This is a language that I came to know and love about a decade ago. It's the scripting language that drives the automated testing tool Eggplant Functional. I was an avid user of the tool for many years before joining the company for a while. It's not the most golf-capable language, but I find it very enjoyable to write in. Golfing in it is actually quite challenging as the language is meant to be verbose and English-like... took me quite a while to get it down to 237 bytes.

set s to "                              +"&lf
set p to s
repeat 30
set a to random(0,2)
if a equals 0
delete first char of p
else if a equals 1
put " " before p
end if
put p after s
end repeat
put s

Ungolfed/Explanation

set the_snake to "                              +"&lf #assign the first line of the snake
set previous_line to the_snake                        #set up for the loop

repeat 30 times                                       #loop 30x
    set action to random(0,2)                         #random add/subtract/stay the same

    if action equals 0
        delete the first character of previous_line   #SenseTalk really shines at string manipulation
    else if action equals 1
        put " " before previous_line                  #insert a character at the beginning
    end if

    put previous_line after the_snake                 #plop the new segment into the string
end repeat                                            #close the loop

put the_snake                                         #print to standard out

Edit: Saved 36 bytes thanks to @mustachemoses

Answer 22

J, 23 bytes

echo(8":~+/)\31,1-?29$3

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Answer 23

PowerShell, 42 bytes

1..($l=30)|%{" "*$l+"x";$l+=-1,0,1|Random}

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Loops from 1 to $l=30. Each iteration we put $l spaces plus an x onto the pipeline as a string, then += either of -1, 0, 1 based on Get-Random into $l for the next loop. Those strings are gathered from the pipeline and an implicit Write-Output gives us a newline-separated list for free.

Answer 24

Jelly, 18 bytes

1ŒRX+
30ǒС⁶ẋ;€0Y

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The chosen character is 0. If returning a list of list of characters is allowed, then the Y can be dropped and the submission can be turned into a niladic chain for 17 bytes. Alternative.

How it works

30ǒС⁶ẋ;€0Y | Niladic main link.
30           | Starting from 30...
  ǒС       | ... Repeat the helper link 29 times and collect the results in a list.
             | (This list includes the first 30, so there are actually 30 numbers).
      ⁶ẋ     | Repeat a space that many times, for each item in the list.
        ;€0  | Append a 0 to each.
           Y | And join by newlines.
-------------+
1ŒRX+        | Monadic helper link. Alternatively, you can use µ1ŒRX+µ instead of the Ç.
1            | The literal one.
 ŒR          | Symmetric range from –1 to 1.
   X+        | Choose a random number therein and add it to the argument.

Jelly, 16 bytes

Combining mine, Erik’s and Jonathan’s solutions, we can golf this down to 16 bytes. The chosen character is 1.

’r‘X
30ǒСṬ€o⁶Y

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Thanks to Jonathan Allan for the heads-up (on Ṭ€o⁶).

Answer 25

Bash, 53

• 3 bytes saved thanks to @Dennis

for((i=p=30;i--;p+=RANDOM%3-1));{ printf %${p}s+\\n;}

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Answer 26

Octave, 53 51 50 49 bytes

printf('%*d\n',[a=31+cumsum(randi(3,1,30)-2);~a])

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Saved 1 byte by no longer doing any looping. Saved another as Octave has printf as well as fprintf.

This new code creates an array of 30 random integers in the range -1:1. It then cumulatively sums the array and adds 30, which gives the desired sequence.

The result is printed using fprintf with a format that says "A decimal number, padded to a specified width, followed by a new line. The width will be the first value input, and the decimal number will be the second value input. If the number of values input is more than this, Octave will keep repeating the print automatically to get the desired output.

To achieve the looping then, we need only interleave zeros between the sequence array so the fprintf function uses each value in the sequence as a width, and each zero as the digit to be printed.

Prints an output like:

                              0
                             0
                              0
                             0
                              0
                               0
                              0
                               0
                              0
                              0
                             0
                            0
                           0
                           0
                           0
                          0
                           0
                            0
                             0
                              0
                              0
                             0
                             0
                              0
                               0
                              0
                              0
                               0
                               0
                                0

---

The above code doesn't always print exactly 30 spaces on the first line. It will be either 29, 30, or 31. To correct that, you would use this 53 byte version:

x=31;for i=2:x;fprintf('%*d\n',x,0);x+=randi(3)-2;end

Answer 27

Python 3.6, 84 73 69 bytes

from random import*
x=30
exec("print(' '*x+'+');x+=randint(-1,1);"*x)

Thanks to @WheatWizard for -11 bytes. Thanks to @JoKing for -4 bytes.

Answer 28

ES5, 97 95 81 bytes

for(p=i=30;i--;)console.log(Array(p).join(" ",r=Math.random()*3|0,p+=r>1?-1:r)+0)

ES5, 112 98 bytes if function format is needed:

function a(){for(p=i=30;i--;)console.log(Array(p).join(" ",r=Math.random()*3|0,p+=r>1?-1:r)+0)}a()

Answer 29

Lua, 81 75 bytes

n=30;for i=1,n do print(("%-"..n.."s+"):format(" "))n=n-2+math.random(3)end

In for i=1,n ... the to_exp n is evaluated only once before entering the loop, saving one byte.

-6 thanks to @user202729

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Answer 30

Red, 54 bytes

loop n: 30[loop n[prin" "]print"+"n: n - 2 + random 3]

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Answer 31

Pyth, 21 19 16 15 bytes

Thanks to Rod for saving 2 bytes and Mr. Xcoder for saving another 3 :)

Uses 0

VK30p*KdZ=+KtO3

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Answer 32

Python 2, 73 bytes

from random import*
l=c=30
while c>0:l+=randint(-1,1);print' '*l+"+";c-=1

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Answer 33

Mathematica, 74 bytes

""<>(" "&~Array~#<>"+
"&)/@Accumulate@Prepend[{-1,1}~RandomInteger~29,30]&

Pure function. Takes no input and returns a string as output.

Answer 34

Julia 0.6, 52 49 bytes

Full program, prints a snake with 0. I usually prefer comprehensions to for...end blocks because comprehensions return things. But since I'm printing anyway this is shorter, and you can use newlines at no cost (meaning equal to ;) for a nice readable golf. Saved a byte by using 1:n instead of 1:30 and two bytes with println(" "^n,0) instead of println(" "^n*"+").

n=30
for i=1:n
println(" "^n,0)
n+=rand(-1:1)
end

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Answer 35

K4, 26 bytes

Solution:

-1(-31+\0,-1+29?3)$\:,"$";

Example:

q)k)-1(-31+\0,-1+29?3)$\:,"$";
                              $
                             $
                             $
                            $
                           $
                            $
                             $
                              $
                              $
                              $
                              $
                              $
                               $
                                $
                               $
                              $
                               $
                              $
                              $
                               $
                                $
                                 $
                                 $
                                $
                                 $
                                $
                               $
                                $
                                $
                                 $

Explanation:

Build a list of negative numbers to left-pad "$", perform padding and print to stdout.

-1(-31+\0,-1+29?3)$\:,"*"; / the solution
-1                       ; / print to stdout and swallow return
                     ,"$"  / enlist "$" (e.g. ["$"])
  (              )$\:      / pad right with each-left
             29?3          / 29 choose 3, takes from 0 1 2
          -1+              / subtract 1, so range is -1 0 1
        0,                 / join 0
      +\                   / sums
   -31                     / add to -31

Bonus:

27 byte version in K (oK):

`0:(-31+\0,-1+29?3)$\:,"*";

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Answer 36

Icon, 51 bytes

-2 bytes thanks to Kevin Cruijssen

n:=30;every 1to 30do{write(repl(" ",n),8);n+:=?3-2}

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Answer 37

Clojure, 88 77 bytes

Always happy to provide a Clojure answer. Always sad, it's quite long.

(loop[x 30 p x](when(> x 0)(printf(str "%"p"d\n")1)(recur(dec x)(+(-(rand-int 3)1)p))))

Ungolfed:

(loop [x 30 p x]
  (when (> x 0) 
    (printf (str "%" p "d\n") 1)
    (recur (dec x) (+ (- (rand-int 3) 1) p))))

Update 1

Managed to shave off 11 bytes by making the code more idiomatic. Who would have thought that making things "more right" would end up being more effective in a Code Golf challenge.

(doseq[p(take 30(iterate #(+ %(-(rand-int 3)1))30))](printf(str "%"p"d\n")1))

Ungolfed:

(doseq [p (take 30
            (iterate
              #(+ % (- (rand-int 3) 1))
              30))]
  (printf (str "%" p "d\n") 1))

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Answer 38

SmileBASIC, 40 bytes

This answer turned out to be pretty boring.

X=30FOR I=1TO 30?" "*X;0X=X+RND(3)-1NEXT

Answer 39

Pip, 21 bytes

Ln:30{PsXn.0--n+:RR3}

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Explanation

                       s is space (implicit)
 n:30                  Set n to 30
L    {              }  Loop that many times:
      P                 Print, with trailing newline:
       sXn               space, repeated n times
          .0             with "0" concatenated
            --n         Decrement n
               +:       and add to it (in-place)
                 RR3    randrange(3), i.e. a random integer between 0 and 2

Answer 40

PHP, 58 56 bytes

for($a=$b=30;$a--;)echo str_pad('',$b+=rand(-1,1))."+
";

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-2 bytes thanks to @Shaggy

Answer 41

Jelly, 18 bytes

30µ3ẋX€_2+\+⁸Ṭ€o⁶Y

Uses 1 as the character.

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Answer 42

Jelly, 17 bytes

30µ’r‘Xµ’С⁶ẋp”.Y

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Full program.

Answer 43

Haskell, 108 bytes

import System.Random
0%_=pure()
n%p=putStrLn(([1..p]>>" ")++"+")>>randomRIO(-1,1::Int)>>=((n-1)%).(p+)
30%30

Try it online! I was surprised to find that this code works in GHCi without the explicit type annotation but not on TIO, until BMO told me about the ExtendedDefaultRules flag which is set by GHCi.

Answer 44

SOGL V0.12, 14 bytes

'∑:{:@*O2ψH+╗p

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Answer 45

AWK, 54 bytes

{for(f=30;a++<30;f+=int(4*rand()-2))printf"%"f"s\n",1}

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Very straightforward. This requires a 1 line input to run. Could make it a "program" by using a BEGIN label.

Answer 46

CJam, 31 bytes

{S*TN}:F;30:V{3,{V1-+}%mRz:VF}*

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Sort of a port of @Datboi's answer

Explanation

{S*TN}:F                         -The padded string function
{                                -Start block
 S*                              -Multiply space string by argument and push to stack
   T                             -Push integer 0 to stack
    N                            -Push newline string to stack
     }                           -End block
      :F                         -Store top of stack(the block) in variable F
        ;                        -Pop from stack
         30:V                    -Push integer 30 to stack and store in variable V
             {3,{V1-+}%mRz:VF}   -The main loop
              3                  -Push integer 3 to stack
               ,                 -Array range from 0 to n-1
                {V1-+}%          -Map to array
                 V               -Push variable V to stack
                  1              -Push integer 1
                   -+            -subtract values from each other and add to array index
                       mR        -Random choice
                         z       -Absolute value
                          :V     -Store in variable V
                            F    - Execute function in F
                              *  -pop stack and repeat block

Answer 47

Go, 123 107 94 bytes

import(."fmt"
."math/rand")
func s(){s:=30
for i:=0;i<30;i++{Printf(`%*d
`,s,4)
s+=Intn(3)-1}}

call function s

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Answer 48

Perl 6, 39 bytes

$_=30;say(" "x($_+=^3 .roll-1)~"x")xx$_

Explanation:

$_=30: Sets the number of spaces to prefix to 30.

say(" "x($_+=^3 .roll-1)~"x"): Outputs that number of spaces and updates it (^3 .roll-1: pick a random integer from 0 to 2 and subtract it by 1), followed by x and a newline.

xx$_: Does this 30 times. Using $_ instead of 30 saves one space before 30.