Invert a boolean array

Question

A nice simple one

Input

Given a boolean array (Or an acceptable alternative), you can assume the array will never be more than 32 elements long.

[false, false, true, false, false]

Output

Invert every element of the array and output it.

[true, true, false, true, true]

Rules

• You can write a full program or just a function
• Standard loopholes apply
• Shortest code in bytes, per language, wins!

Test cases

Input:
[true, false]
Output:
[false, true]

Input: //Example of acceptable alternative
[0,1,1]
Output:
[1,0,0]

Answer 1

05AB1E, 1 byte

Code:

_

Explanation:

_     # Logical not

Try it online!

Answer 2

Jelly, 1 byte

¬

Try it online!

¬ is logical NOT (1 if false-y, else 0). C (“complement”, 1−z) also works.

Answer 3

Javascript ES6, 15 bytes

a=>a.map(b=>!b)

Not much explanation needed I guess

f=
a=>a.map(b=>!b)

a.innerHTML = `[true, false, 1, 0] => ${ f([true, false, 1, 0]) }`

<pre id=a>

Answer 4

Matlab, 4 1 byte

This should be self explanatory.

~

Matlab has the one-byte negation operator ~, if you want a function you can use @not.

Answer 5

Haskell, 7 bytes

map not

Example:

Prelude> (map not) [False, True, True]
[True,False,False]

Answer 6

MATL, 1 byte

~

Try it online!

~ is the logical not and as many functions, it can also be applied to arrays/matrices.

Answer 7

R, 1 byte

!

Example:

> !c(TRUE, FALSE)
[1] FALSE  TRUE

It also works with numerical input:

> !c(1, 0)
[1] FALSE  TRUE

We're not restricted to one-dimensional arrays, either. Let's make a matrix, and randomly populate it with 0s and 1s:

> mat = matrix(rbinom(16, 1, .5), ncol=4)
> mat
     [,1] [,2] [,3] [,4]
[1,]    0    1    1    1
[2,]    0    1    0    0
[3,]    0    0    0    0
[4,]    1    1    1    0

We can invert this just as easily:

> !mat
      [,1]  [,2]  [,3]  [,4]
[1,]  TRUE FALSE FALSE FALSE
[2,]  TRUE FALSE  TRUE  TRUE
[3,]  TRUE  TRUE  TRUE  TRUE
[4,] FALSE FALSE FALSE  TRUE

We can continue to do this for arbitrary numbers of dimensions. Here's an example on a four-dimensional array:

> bigarray = array(rbinom(32, 1, 0.5), dim=c(2,2,2,2))
> bigarray
, , 1, 1

     [,1] [,2]
[1,]    0    0
[2,]    0    0

, , 2, 1

     [,1] [,2]
[1,]    1    0
[2,]    0    0

, , 1, 2

     [,1] [,2]
[1,]    0    1
[2,]    0    1

, , 2, 2

     [,1] [,2]
[1,]    1    0
[2,]    1    1

> !bigarray
, , 1, 1

     [,1] [,2]
[1,] TRUE TRUE
[2,] TRUE TRUE

, , 2, 1

      [,1] [,2]
[1,] FALSE TRUE
[2,]  TRUE TRUE

, , 1, 2

     [,1]  [,2]
[1,] TRUE FALSE
[2,] TRUE FALSE

, , 2, 2

      [,1]  [,2]
[1,] FALSE  TRUE
[2,] FALSE FALSE

Doesn't work for characters, I'm afraid.

> !"Hello world"
Error in !"Hello world" : Invalid argument type.

Answer 8

C, 46 Bytes recursive version

f(char*s){*s?putchar(*s&72?*s:*s^1),f(++s):0;}

C, 47 Bytes iterative version

f(char*s){for(;*s;putchar(*s&72?*s:*s^1),s++);}

Run using this main function

main(c,v)char**v;
{
    f(v[1]);
}

and input like this

a.exe [1,0,1,1,0]
[0,1,0,0,1]

Answer 9

Perl 6, 4 bytes

"French"/Unicode version:

!«*

"Texas"/ASCII version:

!<<*

Input is a single value which can be treated as a list.

This is a a Whatever lambda (*) with the logical not prefix operator (!) combined using prefix hyper operator («).

Effectively this is the same as:

-> $_ { $_.values.hyper.map: &prefix:<!> }
# ( currently the Rakudo implementation doesn't actually do the ｢.hyper｣ call,
#   but prefix ｢«｣ is specifically designated for doing things in parallel )

Usage:

# pretend it's a method
say (True,False,True,True).&( !«* );
# (False True False False)

say ( !«* )( (False,False,True,False,False) );
# (True True False True True)


# give it a lexical name
my &list-invert = !«*;

#              v¯¯ a space is necessary here
say list-invert (True,False);
# (False True)

say (False,True).&list-invert;
# (True False)

Answer 10

Labyrinth, 9 bytes

,$:)%#$.,

Try it online! Assumes newline-separated input with a trailing newline. Thanks to @MartinEnder for help with golfing.

This program's a bit weird for a Labyrinth program - it doesn't make use of the 2D nature of the language, and it actually bounces back and forth. On the first forward trip, we have:

[Moving rightward]
,            Read char c of input
 $           XOR c with implicit 0 at bottom of stack
  :)%        Calculate c % (c+1), erroring out if c == -1 from EOF, otherwise returns c
     #$      XOR with (length of stack == 1)
       .     Output (c^1) as char
        ,    Read newline

[Moving leftward]
       .     Output newline
      $      XOR two implicit 0s, stack [0]
    %#       Mod with (length of stack == 1), giving stack [0]
 $:)         Increment, duplicate then XOR, stack still [0]
,            Read char c of input

The next occurence of $ then XORs the existing 0 on the stack with c, as opposed to an implicit 0 at the bottom of the stack like in the first run. Both situations leave the stack as [c], and the program repeats thereafter.

Alternative 9-bytes:

,:):/$.:,
,::)/)$.,
,:):%)$.,

Answer 11

Mathematica, 7 bytes

Not/@#&

or without letters:

!#&/@#&

As for the syntactic sugar: & marks the right end of an unnamed function and has very low precedence. # refers to the first argument of the nearest and enclosing &. ! is the operator for Not. So !#& is just an unnamed function that negates its argument, in other words its identical to the built-in Not. /@ is the operator for Map. So the code would also be equivalent to the somewhat more readable Map[Not, #]&.

Answer 12

Python, 27 25 24 bytes

Thanks to Lynn for golfing off two bytes, and xnor and Mego for golfing off another.

lambda a:[b^1for b in a]

Answer 13

C#, 19 bytes

as an annonymous function, takes a bool[] and returns an IEnumerable

b=>b.Select(x=>!x);

or in 36 bytes with

dynamic f(bool[]b)=>b.Select(x=>!x);

Answer 14

IBM/Lotus Notes Formula, 2 bytes

!a

Usage:

Create a Notes form with two fields named a and b.

a (input) = editable, number, multi-value, comma separated

b (output) = computed, number, multi-value, comma separated

Paste the above formula into b and give a a default value of 0.

Create a new document with the form, enter a binary list in a and press F9 to update the output.

Examples:

Works because given a list as input, Notes formula will apply whatever specified action to every element in the list.

Answer 15

J, 2 bytes

-.

This is the negation verb.

Test case

   -. 0 1 0 0 1
1 0 1 1 0

Answer 16

Swift 3 (7 bytes)

.map(!)

e.g.

[true, false].map(!)

Explanation

Seems pretty obvious. Calls map on the array [true, false]. The one "gotcha" is that, in Swift, operators are just functions and can be passed around as arguments. This means map(!) is passing the "not" function ! into map.

Answer 17

Shakespeare Programming Language, 240 bytes

.
Ajax,.
Puck,.
Act I:.
Scene I:.
[Enter Ajax and Puck]
Puck:
Open your mind.Is hog as big as you?If so, let us return to scene II.You be sum of difference of zero and you and cat.Open thy heart!Let us return to scene I.
Scene II:.
[Exeunt]

Takes input as a string of \0 and \1 control characters. Outputs as a string of 0 or 1. If the input must be the same as the output, replace Open thy heart with Speak thy mind for no change in bytecount. If \0 and \1 can't be used, do the above, but also replace Open your mind with Listen to thy heart for a 5-byte penalty.

Ungolfed:

The Invertion of Veronan Arrays.

Romeo, who stores the element.
Juliet, who lectures him.

Act I: In which an array is inverted.

Scene I: A silent entrance.

[Enter Romeo and Juliet]

Scene II: In which Juliet pours out her heart to Romeo.

Juliet:
  Open your mind. Is nothing better than thee? If so, let us proceed to scene III. 
  Thou art as good as the sum of the difference between nothing and thee and my 
  cat. Open your heart! Let us return to scene II.

Scene III: Finale.

[Exeunt]

This roughly translates to the following C pseudocode:

int romeo;

Scene1:
romeo = getchar();
if (0 > romeo) goto Scene2;
romeo = 0 - romeo + 1;
printf("%d", romeo);
goto Scene1;

Scene2:;

I'm using this interpreter. Sample run:

$ python splc.py invert.spl > invert.c
$ gcc invert.c -o invert.exe
$ echo -ne "\x00\x01\x00" | ./invert
101

Answer 18

JAISBaL, 1 byte

!

Like all the other 1-byte answers, this is the negation operator, which can operate over an array if needed. This leaves the output on the stack, which is printed at the end of the program.

For two bytes, the array can be explicitly printed:

!§

Input is in JAISBaL's incredibly odd array format (which I did invent, but I don't like it...).

Test Cases (Output from the Java interpreter, 3.0.5):

Enter a value > [true][false]


--------------------
Stack: [[false, true]]
Locals: {}
----------------------------------------
Enter a value > [false][false][true][false][false]


--------------------
Stack: [[true, true, false, true, true]]
Locals: {}

Answer 19

PowerShell, 15 bytes

$args[0]|%{!$_}

I think this may even work in v1, hence I left the version number off the title. Loops through the input $args and negates each item in turn. That resulting array is left on the pipeline.

The neat thing, however, is because PowerShell is so loose on its casting requirements, you can do a completely mixed input and get an appropriate Boolean output. For example, here are the literal Boolean values $false/$true, the numbers 0 1 and 123456789 as integers, an empty string, a non-empty string, an empty array, and a non-empty array --

PS C:\Tools\Scripts\golfing> .\invert-a-boolean-array.ps1 @($false,$true,0,1,123456789,'','foo',@(),@(1,1))
True
False
True
False
False
True
False
True
False

Answer 20

Perl, 7 bytes

Includes +2 for -lp

Give each boolean value as 0 or 1 on its own line

invert.pl
1
1
0
^D

invert.pl:

#!/us/bin/perl -lp
$_^=1

Answer 21

Logicode, 9 8 bytes

out!binp

Simple, really.

Takes input as a binary string, as Logicode doesn't have support for lists (so [true, false] would be 10).

The out outputs the line's result.

The ! command calculates the NOT of every bit in the string, so something like !111 would be 000.

The binp is binary input.

1 byte saved thanks to @daHugLenny

Answer 22

Brachylog, 7 bytes

:{-$_}a

Try it online!

Explanation

:{   }a   Apply this predicate to each element of the Input
  -         Decrement
   $_       Negate

Answer 23

Java, 58 bytes

void f(boolean[]a){for(boolean i:a)System.out.print(!i);}

Answer 24

Cheddar, 10 bytes

@.map((!))

I hope I counted right as I'm writing from phone

Answer 25

brainfuck (58 Bytes)

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

Try it here

Ungolfed

-[>+<-----]>---     Number 48 (stands for 0)
>,                  Read in first point
[               
    <[->->+<<]      Subtract 1 from 48 flag, subtract 1 from read data, add 1 for new flag
    >           
    [--<]           If sitting on 1 (true) subtract 2 and move left)
        >[>]<       Move to 48 flag
        [-<+<+>>]   Add 48 to data point
        <+.[-]<     Add 1 move print, zero cell, move to new 48 cell
        >,          Read in next point
]                   Loop if input remaining

Takes an input of undivided 1s or 0s (11001).

Answer 26

CJam, 4 bytes

{:!}

Input is a list of 0s and 1s.

Try it online!

Answer 27

Japt, 3 bytes

¡!X

Japt doesn't have boolean input, so input is an array of 0s and 1s. Test it online!

How it works

¡    // Map each item X in the input to
 !X  //  the boolean NOT of X.
     // Implicit output

Answer 28

Retina, 3 bytes

%`0

Try it online!

For each line (%), count the number of 0s.

Answer 29

Python 2, 24 bytes (non-competing)

lambda a:[i-1for i in a]

Logic is similar to Steven's, but I tried to use this comment's idea, but different, because it still takes 0/1 arrays, not 0/-1. There is no byte shaving for using 0/-1, so let's be sane. Note that this is non-competing, until Steven or Lynn allows me to use the idea. If so, I might remove the non-competing mark. Note that this code cannot be shamelessly stolen, it's still here. Only Steven can use it for his answer.

Answer 30

Ruby, 14 bytes

Anonymous function:

->a{a.map &:!}

Test it:

->a{a.map &:!}.call([true, true, false, true, false, true, true])
# => [false, false, true, false, true, false, false]

Answer 31

Julia (1 Byte - Thanks to Dennis [See Comments])

!

Map the logical not to all elements of collection y, works due to automatic vectorization (as Dennis explained). My previous answer was basically using `f(n)=map(!,n)' to map the logical not, but Julia does this on it's own. Jeez, what a cool language. Second time using it, still trying to learn here!

Try it here

Answer 32

Perl 6, 9 bytes

*.map: !*

Usage:

say (*.map: !*)((0, 1, 1)) # (True False False)

Answer 33

Actually, 2 bytes

♂Y

Try it online!

Map (♂) Boolean negate (Y)

Answer 34

Clojure, 12 bytes

#(map not %) 

Basically the same as the Haskell answer. Unfortunately, Clojure doesn't have implicit partial application; thus the function macro.

Answer 35

Java, 15 bytes

s->s.map(b->!b)

Note: s is a java.util.stream.Stream<Boolean> and the import is not necessary, proof below.

Testing and ungolfed

LookMaNoImports.java

class LookMaNoImports {
  static Main.F f = s -> // transform a Stream<Boolean>
    s.map(               // by applying its map method
      b ->               // which in turns transforms a boolean 
        !b               // by applying its negation.
    );
}

Main.java

    import java.util.Arrays;
    import java.util.List;
    import java.util.stream.Collectors;
    import java.util.stream.Stream;

    public class Main {

        interface F {
            Stream<Boolean> f(Stream<Boolean> s);
        }

        public static void main(String[] args) {
            F f=LookMaNoImports.f;

            test(f, new Boolean[]{true}, new Boolean[]{false});
            test(f, new Boolean[]{false}, new Boolean[]{true});
            test(f, new Boolean[]{true, false}, new Boolean[]{false, true});
            test(f, new Boolean[]{true, true}, new Boolean[]{false, false});
        }

        static void test(F f, Boolean[] param, Boolean[] expected) {
            List<Boolean> result = f.f(Arrays.stream(param)).collect(Collectors.toList());
            if (result.equals(Arrays.asList(expected))) {
                System.out.printf("%s: OK%n", Arrays.toString(param));
            } else {
                System.out.printf("%s: NOT OK, expected %s%n", Arrays.toString(param), Arrays.toString(expected));
            }
        }
    }

Answer 36

Pyth, 2 bytes

!M

Explanation: (M)ap boolean not (!) over input.

Try it online!

Answer 37

Hoon, 24 bytes

|*
*
(turn +< |=(? !+<))

Creates a generic gate, map over the contents of the list, negate all loobeans in it.

This uses the normal Hoon tricks, namely using a generic ("wet"/|*) gate to avoid having to specify the sample type, along with having unnamed samples (* or ?) and using tree navigation syntax (+<) to fetch them.

> a 
~[%.y %.n %.n %.y %.n %.y] 
> =f |* 
  * 
  (turn +< |=(? !+<)) 
> (f a) 
~[%.n %.y %.y %.n %.y %.n] 

Answer 38

braingasm, 9 bytes

,[48-z:,]

Assumes that input from stdin is a string of only "0"s and "1"s, i.e. bytes containing the value 48 or 49. Prints the negated values to stdout.

How it works: Read one byte from stdin (,), and loop ([]) until the end of the input. For each byte, subtract 48 (48-) and print 1 if the result is 0 and vice versa (z is the zero-flag, : prints the given integer value), then get another byte from stdin (,)

Run it like e.g. $ echo -n 001011 | braingasm invert.bg and get 110100

Answer 39

Groovy (19 Bytes)

{x->x.collect{!it}}

Simple mapping function in a closure.

Answer 40

Clojure, 12 bytes

(map not x)

as in:

(map not [true false true])

=> (false true false)

Updating due to the objection that this is not a function or program:

#(map not %)

Returns a function that nots anything passed to it.

Answer 41

Stata, 20 bytes

recode x (0=1) (1=0)

x is the input, and the rest is self-explanatory

Answer 42

Scala, 27 bytes

def f(a:Boolean*)=a map(!_)

Takes a bool array as varargs and maps each element to its inverse.

Answer 43

Kotlin, 13 bytes

{it.map{!it}}

This is a lambda of (List<Boolean>)->List<Boolean> type (or (BooleanArray)->List<Boolean>, as map function on arrays returns lists instead of arrays).

{it.map{!it}.toBooleanArray()} would return the result as an actual array.

Answer 44

sed 8

y,01,10,

Takes input as 1s and 0s.

Answer 45

Scala, 36 35 34 bytes

def f(a:Array[Boolean])=a.map(!_)

Discovered I could remove the second space. Discovered I could remove brackets.

Answer 46

Gogh, 4 bytes

{!}m

Usage:

$ ./gogh -noa '{!}m' "1 0 1 0 0 0 1"
[0 1 0 1 1 1 0]

Answer 47

Racket, 15 bytes

(curry map not)

Basically the Haskell answer.

Answer 48

Pyke, 2 bytes

m!

Try it here!

map(not, input)

Answer 49

Golang, 40 bytes

func(a[]bool){for i,b:=range a{a[i]=!b}}

usage

package main
import "fmt"
func main() {
    a:=[]bool{true, true, false}
    func(a []bool){for i,b:=range a{a[i]=!b}}(a)
    fmt.Print(a) // => [false false true]
}

Answer 50

PHP, 30 bytes

foreach($argv[1] as$i)echo!$i;

Testing code:

$argv[1] = [true,true,false,true,false,false,true,false];
foreach($argv[1] as$i)echo!$i;

Test online

Answer 51

C++11, 30 bytes

As unnamed lambda:

[](auto&v){for(auto&x:v)x=!x;}

Accepts any standard container like vector<int> (but not vector<bool>) or int[] or bool[].

Answer 52

SmileBASIC, 25 bytes

DEF l l
ARYOP 1,l,1,l
END

Explanation:

DEF 'create a function
    l 'named "L"
      l 'with 0 outputs and 1 input named "L"
ARYOP 'array operation
      1 'mode 1 (subtract)
       ,l 'set each element in L to...
         ,1 '1 minus...
           ,l 'the corresponding element in L
END 'end function definition

Answer 53

FALSE, 13 bytes

[49^$0>][-.]#

Input is a list of 0 and 1 characters.

Answer 54

Tcl, 31 bytes

proc N L {lmap b $L {expr !$b}}

Try it online!

Answer 55

PHP , 45 Bytes

<?foreach($_GET[a]as$v)$a[]=1-$v;print_r($a);

Answer 56

Java, 51 bytes

l.stream().map(b->!b).collect(Collectors.toList());

l = a Collection of Booleans I feel like this could be shorter, then again golfing in java ^^

Answer 57

 Common Lisp, 7

bit-not

Negate bits on a bit array.

Example

(bit-not #*00101010010100101001010010101)
=> #*11010101101011010110101101010

Answer 58

Ruby, 30 bytes

gets.split(?,).map{|e|!eval e}

"true,false" outputs false,true.

Answer 59

Swift(2.2) 44 bytes

I am using x as the input variable here. For example,

let x = [true,false]

¯\_(ツ)_/¯

Golfed

let y = {let b = $0.map({!$0});print(b);}(x)

unGolfed

let y = {
   let b = $0.map({!$0})
   print(b);
}(x)

Answer 60

PHP (231 Bytes)

function flip_bool_array($array) {
  $newarray = array();
  foreach ($array as $bool) {

   if ($bool === true) {
    $bool = false;
   } else {
    $bool = true;
   }

  $newarray[] = $bool;

}

return $newarray;

}

Explanation

The function accepts an array and loops over it testing each value for a true value and setting it to false, if the value is not true then it is set to true. Each boolean is added to a new array and returned.

Answer 61

dc, 44 bytes

Append this to a line of space-delimited input and echo it into dc. Output is delimited with newlines and punctuated with error messages (due to the blatant abuse of k). If you quote the stuff, it'll give you even more errors. (When we re-vamp dc in the next version, we should probably do something about that.) I suggest pairing with a 2>nul or other system-specific hack for suppressing whiny programs.

0sz[1r-SAlz1+szz0<a]dsax[lzd1-szLApk0<a]dsax

Explained:

              # "ToS" := "top of stack"
0sz           # Initialise register `z' with 0: this will hold the length of our input
[             # Open macro definition
 1r-          #  Replace ToS with !(ToS): 1-1==0, 1-0==1
 SA           #  Store this result on the top of stack `A'
 lz1+sz       #  Increment z, our length counter
 z0<a         #  If the stack depth is positive, repeat (we still have input to negate)
]dsax         # Store a copy of macro in register `a' and execute it
              # At this point, our input has been negated and stored in A,
              #  first-in-first-out orientation
[             # Open macro definition
 lzd1-sz      #  Decrement z and keep a copy of it for later
 LA           #  Push ToS(A) onto stack; pop from A
 p            #  Peek at ToS
 k            #  `k' is for KILL THE TOP OF STACK BWAHAHAHA
 0<a          #  The value from register `z' is now on top: if positive, we still have
              #   values to print, so repeat macro
]dsax         # I'm in a chaotic mood, so let's just re-use `a'

Answer 62

dc, 47 bytes

?zsN0sI[z:az0<A]dsAx[lI1+ddsI;a1r-n32PlN>R]dsRx

The actual code to invert a boolean (0 or 1) is 1r-. The rest is for reading the list and printing it in the same order, which is quite hard because of the (LIFO) stack that dc uses to store the input.

Explanation:

?zsN0sI         # read input, LIFO, initialize N = nr_elements and I = 0 (iterator)
[z:az0<A]dsAx   # loop A: move the stack content into array 'a' (I add a[n] first,
                #then a[n-1], ..., then a[1] and a[0] is not used)
[lI1+ddsI;a     # loop R: increment iterator and push a[I] to stack (input order)
   1r-n32P         #invert value and print it with a space separator
lN>R]dsRx       #repeat (R)

Run:

dc -f invert_boolean.dc <<< "1 0 1 1"

Output: there is a trailing separator (space) at the end, but I hope that's ok

0 1 0 0 

Note: my answer is similar in concept to that of @Joe's, but there are differences in terms of I/O handling, stack manipulation (I use arrays) and lack of warnings. Do check his answer as well.

Answer 63

Emacs Lisp, 25 bytes

(lambda(x)(mapcar'not x))

Not very creative.

Answer 64

Racket 11 bytes

(map not l)

Testing:

(define l '(#t #f #t)) ; define a list of booleans

(map not l)

Output:

'(#f #t #f)

Answer 65

><> Fish - 9 (16?) Bytes

My second golf and my first in ><> Fish!

l?!;r0=nr

I'm not sure how to count bytes when flags are considered, but this solution works when running the python interpreter with the -v flag and then space-separated 1's and 0's. If this doesn't match spec, I can remove the answer.

Example

Input/Run:

python fish.py --code "l?!;r0=nr" -v 0 1 0 1 1

Output:

10100

If I'm not allowed to use flags, and instead need to take the input from the input stack (such as on https://fishlanguage.com/playground), the code becomes longer as I must read from the input stack (either 1 or 0 without any separation) until there are no more values, and then convert the char value of the input (1 becomes 49 and 0 becomes 48) to their decimal values before my comparison. I'm not sure how to count bytes for ><> but I believe this would be 16 bytes.

i:1+?!;f3*3+-0=n

Answer 66

Brainfuck, 72 69 61 bytes

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

Closest i managed to get as BF dosent have Array support

Formatting is stupid, i will fix it when i get a pc... Somehow it wont let me post it as a snippet

Answer 67

Brainfuck, 24 bytes

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

Try it online!

The same as my answer to a similar question.

Relies on 8-bit wrapping cells, the cell size might not matter (untested) but wrapping definitely is. The main part the program is the >++[->++[<]>-]>- does some rather convoluted things to flip the last bit of the number.

A shorter solution of 19 bytes is

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

but this requires the < to noop if the data index is 0, instead of the more typical implementation of going into negative indeces.

Answer 68

dimwit 8 bytes (non-competing)

R1,0}0,1

Replaces all 0's with 1's, and vice versa.

Takes input through a string of 0's and 1's, and outputs similarly. Hopefully that's acceptable ;)

Try it here!