Adding up the digits and the digits reversed

Question

Given a number > 0, output the sum with all digits (1 .. n) concatenated and reversed and add them up. For example, with n = 6:

The numbers 1 to 6 concatenated:

123456

Reversed:

654321

Adding them up together will result in: 777777. Another example is n = 11:

1 2 3 4 5 6 7 8 9 10 11 > 1234567891011

and

11 10 9 8 7 6 5 4 3 2 1 > 1110987654321

Adding them up together will result in 2345555545332. This is also known as A078262.

Shortest code wins!

Answer 1

05AB1E, 7 bytes

LDRJsJ+

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Explanation

LDRJsJ+

L        range from 1 .. input
 D       duplicate
  R      reverse
   JsJ   convert both arrays to strings
      +  add (coerces both strings to ints)

Answer 2

Jelly, 9 bytes

R,U$DF€ḌS

 

Answer 3

CJam, 15 14 bytes

Thanks to Martin for shaving a byte!

ri,:)_W%si\si+

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Answer 4

Pyth, 12 10 bytes

ssMjLk_BSQ

Thanks to @FryAmTheEggman for 2 bytes!

Q is the input, S turns it into [1, 2, ..., input()], _B bifurcates it over _ (reverse) to create [rng, rev(rng)], jLk maps it over join by k (which is the "empty string" variable), sM maps int over this resulting array, and s finally calculates the sum.

Answer 5

Python 3, 74

Saved 6 bytes thanks to DSM.

Nothing too exciting, join the ranges and then convert to ints and add them.

lambda x:sum(int(''.join(list(map(str,range(1,x+1)))[::i]))for i in(1,-1))

Answer 6

JavaScript (ES6), 70 67 64 bytes

a=>(z=[...Array(a)].map((b,c)=>c+1)).join``- -z.reverse().join``

Fixed to meet requirement, as old code was made under misunderstanding of the input.

Answer 7

Retina, 71

• 7 bytes saved thanks to @daavko.
• 3 bytes saved thanks to version 0.7.3 features

Because its blatantly the wrong tool for the job.

.+
$*a:$&$*
+`^(a+)a\b(.*)\b1(1+)$
$1 $& $3
 ?(\w)+ ?
$#1
\d+:?
$&$*c
c

Try it online.

Works for inputs up to 6, but the online interpreter times out after that.

Answer 8

Jolf, 9 bytes

Try it here! Replace ► with \x10.

+P►γzjP_γ
    zj    range 1...j
   γ      γ = ^
  ►        ^ .join("")
 P         as a number
+     P_γ  and γ reversed

I may be able to golf it by moving around the type casting.

Answer 9

JavaScript (ES6), 67 66 bytes

n=>(a=[...Array(n+1).keys()].slice(1)).join``- -a.reverse().join``

Yes, that's a space. Ugh. At least @Downgoat helped me save a byte.

Answer 10

Vyxal s, 5 bytes

ɾḂWvṅ

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ɾ         range: [1 .. x]
 Ḃ        pop x, push x, reversed(x) [bifurcate]
  W       wrap the stack
   v      for each
    ṅ     join on ""

s (flag)  sum

-2 bytes thanks to Razetime

Answer 11

Seriously, 12 bytes

,R;Rεj≈@εj≈+

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Explanation:

,R;Rεj≈@εj≈+
,R;           push two copies of range(1, input()+1)
   R          reverse one copy
    εj≈@εj≈   concatenate both and cast both to ints
           +  add
         

Answer 12

PowerShell, 35 bytes

param($a)+-join(1..$a)+-join($a..1)

Converts the input to ranges with .., then -joins them together, and adds 'em up.

Will work for input numbers up to 138, while 139 will give Infinity, and 140 and above will barf out an awesomely verbose casting error:

Cannot convert value "12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273
747576777879808182838485868788899091929394959697989910010110210310410510610710810911011111211311411511611711811912012112212312412512612712812913013113213313413
5136137138139140" to type "System.Int32". Error: "Value was either too large or too small for an Int32."

Answer 13

Pyth - 8 bytes

siRT_BSQ

Try it online here.

Answer 14

JavaScript (ES6), 99

This adds digit by digit, so it can handle numbers well above the 53 bits of precision of javascript

n=>eval("for(a=b=c=r='';n;a+=n--)b=n+b;for(i=a.length;i--;r=c%10+r)c=(c>9)-(-a[i]-b[i]);c>9?1+r:r")

Test

f=n=>eval("for(a=b=c=r='';n;a+=n--)b=n+b;for(i=a.length;i--;r=c%10+r)c=(c>9)-(-a[i]-b[i]);c>9?1+r:r")

// Less golfed
U=n=>{
  for(a=b=c=r=''; n; --n)
      b=n+b, a+=n;
  for(i=a.length; i--; r = c%10+r) 
      c=(c>9)-(-a[i]-b[i]);
  return c>9? 1+r : r;
}

function test() {
  var n=+I.value
  R.textContent=f(n)
}  

test()

N: <input id=I value=11 oninput="test()"> -> <span id=R></span>

Answer 15

Brachylog, 24 bytes

:1fLrcC,Lc+C=.,{,.:1re?}

Answer 16

MATL, 13 bytes

:tP2:"wVXvU]+

EDIT (May 20, 2016) The code in the link uses Xz instead of Xv, owing to recent changes in the language.

Try it online!

:                % range [1,2,...,n], where n is input
 tP              % duplicate and flip
   2:"     ]     % do this twice
      w          % swap
       V         % convert array of numbers to string with numbers and spaces
        Xv       % remove spaces
          U      % convert to number
            +    % add the two numbers

Answer 17

05AB1E, 5 bytes

LJDR+

Explanation:

L     # Pushes an array containing 1 .. [implicit] input
 J    # Join the array to a string (eg. [1, 2, 3] -> 123)
  D   # Duplicate the array
   R  # Reverse the duplicate
    + # Add them together

Try it online!

Answer 18

Bash + coreutils, 39

eval echo {1..$1} + {$1..1}|tr -d \ |bc

Or:

bc<<<`eval printf %s {1..$1} + {$1..1}`

Ideone.

Answer 19

Perl 6, 25 bytes

{([~] @_=1..$^n)+[R~] @_}

{
  (
    [~]           # reduce with the string concatenation infix op:
    @_ = 1 .. $^n # the range 1 to input ( also stored in @_ )
  )
  +               # add that to
  [R~] @_         # @_ reduced in reverse
}

Usage:

for 6, 11, 12 -> $n {
  say {([~] @_=1..$^n)+[R~] @_}( $n )
}

777777
2345555545332
244567776755433

Answer 20

R, 34 60 64 bytes

f=pryr::f;g=f(as.numeric(paste(x,collapse='')));f(g(1:n)+g(n:1))

Assumes pryr package is installed. this gives f as a shorthand for creating functions.

Edit added 26 bytes but returns a function that works, not something entirely wrong.

Edit added another 4 bytes to handle cases above n=10 where strtoi (previously used) was returning NA

Answer 21

Lua, 57

a=''b=''for i=1,...do a=a..i b=b.. ...-i+1 end return a+b

Answer 22

Lua, 53 Bytes

This program takes n as a command-line argument.

s=""r=s for i=1,arg[1]do r,s=i..r,s..i end print(s+r)

I assumed that outputing a number with a decimal part of 0 was okay (in the form 777777.0 because this is the default way to output a number in lua (there's no distinction between integer and float)

Answer 23

Perl 5, 37 bytes

25 bytes, plus 1 for -p and 11 for -MList::Gen

$_=<[.]1..$_>+<[R.]1..$_>

---

Previous solution, 40 bytes: 39, plus one for -p

@a=reverse@_=1..$_;$"=$\;$_="@a"+"@_"

Answer 24

Perl, 36 bytes

Includes +1 for -p

Run with on STDIN

perl -p reverse.pl <<< 6

reverse.pl

$_=eval join"",map{abs||"+"}-$_..$_

Answer 25

Haskell, 57 56 48 bytes

This could probably be golfed a bit more, but here it goes:

f x=read y+(read.reverse$y)where y=[1..x]>>=show

Edit: shaved off a space before the where.

Answer 26

Dyalog APL, 17 bytes

+/⍎¨∊¨⍕¨¨x(⌽x←⍳⎕)

⎕ prompt for input
⍳' enumerate until input
x← store list in x
⌽ reverse x
x(…) prepend reversed list with original list
⍕¨¨ convert each number of each list into character string
∊¨ make each list of character strings into single character strings
⍎¨ convert each character string into a number
+/ sum the two numbers.

Answer 27

Factor, 59 bytes

[ [1,b] dup reverse [ [ present ] map concat dec> ] bi@ + ]

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• [1,b] Create a range from 1 to the input, inclusive.
• dup reverse Make a copy and reverse it.
• [ [ present ] map concat dec> ] bi@ Convert them both to numbers of concatenated numbers.
• + Add.

Answer 28

Python 3, 79 bytes

a=''.join([str(i+1) for i in range(int(input()))])
print(int(a)+(int(a[::-1])))

Try it online!

Answer 29

Thunno 2 s, 4 bytes

RJNḲ

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Explanation

RJNḲ  # Implicit input
R     # Push [1..input]
 J    # Join into a string
  N   # Convert to integer
   Ḳ  # Duplicate and reverse
      # Sum the stack
      # Implicit output

Answer 30

Mathematica, 64 bytes

Plus@@FromDigits/@#&[""<>ToString/@#&/@{#,Reverse@#}&[Range@#]]&