Challenge

For each character of the string except for the last one, do the following:

• Output the current character.



• 
  

  Followed by randomly outputting from the following list a random number of times between 1 and 5 (inclusive):

  
  
  
  
  
  • The current character
  
  
  • The next character of the string
  
  
  • The switchcase version of the character that you are currently on
  
  
  • The switchcase version of the next character of the string.
  
  
  
  

Test Cases

String --> SSSTSStrTrIiinIIngn

, . , . , . Hello world! --> ,,, .. , ,, .... , , .. .. . HHH HHEeelLlLllooO wwOworOOrrrRllDd!!D

Programming Puzzles and Code Golf --> PrPPrRrOooooogggRgGraAraaaMMMmmmimMIiininGGgG PPPPuZzZZzZzzZzllLLEEeEsEsssS a aANnNddD C COCoooOOdeDe E GGGoOllFFf

Notes

• You only need to apply the upper/lowercase form of a character if the character is part of the upper/lowercase alphabet (A-Z/a-z).


• Your random function does not need to be uniform but it still needs to have a chance of returning any element in the list given.


• You are allowed to use any standard I/O format.


• You may assume that the length of the input is greater than or equal to two.


• You may assume that the input only consists of ASCII characters.

Gaia, 21 bytes

ṅ@ṇ+†⟨(₌¤:~+ṛ5ṛ&⟩¦$

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ṅ			| delete the first character from the input

  @ṇ			| push the input again and delete the last character

     +†			| concatenate together, so for example 'abc' 'bcd' becomes ['ab' 'bc' 'cd']

       ⟨           ⟩¦	| for each of the elements, do:

	(₌		| take the first character and push again

	  ¤		| swap

	   :		| dup

	    ~		| swap case

	     +		| combine strings

	      ṛ		| select a character at random

	       5ṛ	| select a random integer from [1..5]

		 &	| run-length decode

		  $	| convert to string

Bash, 150 bytes

Have done very little golf bashing and trying to improve my bash, so any comments welcome.

for((i=0;i<${#1}-1;i++));do

c=${1:$i:1}

n=${1:$((i+1)):1}

a=($n ${c,} ${c^} ${n,} ${n^})

shuf -e ${a[@]} -n "$(shuf -i 1-5 -n 1)"|xargs printf %s

done

Try it online!

Code is straightforward loop through chars setting current c and next n character, then creating an array of the 4 possibilities, repeating one of them so there's exactly 5. Next we shuffle that array, and then choose n elements from it, where n itself is random between 1 and 5.

APL (dzaima/APL), 19 bytes

Anonymous tacit prefix function.

∊2(⊣,{?5⍴4}⊇,,-⍤,)/

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2(…)/ apply the following infix tacit function between each character pair:

 - the switchcase

 ⍤ of

 , the concatenation of the pair

 ,, prepend the concatenation of the pair to that

 {…}⊇ pick the following elements from that:

  5⍴4 five fours

  ? random indices for those

∊ ϵnlist (flatten)

Charcoal, 27 bytes

ＦＬθ«Ｆ∧ι⊕‽⁵‽⭆✂θ⊖ι⊕ι¹⁺↥λ↧λ§θι

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

ＦＬθ«

Loop over all of the indices of the input string.

Ｆ∧ι⊕‽⁵

Except for the first index, loop over a random number from 1 to 5 inclusive...

‽⭆✂θ⊖ι⊕ι¹⁺↥λ↧λ

... extract the previous and next characters from the string, take the upper and lower case versions, and pick a random character of the four.

§θι

Print the character at the current index.

Japt v2.0a0, 43 bytes

s0UÊÉ)rÈ+Y+(C=[Yu Yv T=UgZÄ v Tu] cMq5 £C ö

After a month of so of Japt, I'm still not very good at it.

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Python 2, 107 bytes

f=lambda s:s and s[0]+''.join(sample((s[:2]+s[:2].swapcase())*5,randint(1,5)))+f(s[1:])

from random import*

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