Test a number for narcissism

Question

A Narcissistic Number is a number which is the sum of its own digits, each raised to the power of the number of digits.

For example, take \$153\$ (3 digits):

\$1^3 + 5^3 + 3^3 = 153\$

\$1634\$:

\$1^4 + 6^4 + 3^4 + 4^4 = 1634 = 1 + 1296 + 81 + 256 = 1634\$

The Challenge:

Your code must take input from the user and output True or False depending upon whether the given number is a Narcissistic Number.

Error checking for text strings or other invalid inputs is not required. 1 or 0 for the output is acceptable. Code that simply generates a list of Narcissistic Numbers, or checks the user input against a hardcoded list, does not qualify.

OEIS A005188

Answer 1

APL (15)

∆≡⍕+/(⍎¨∆)*⍴∆←⍞

Outputs 1 if true and 0 if false.

Explanation:

• ∆←⍞: read a line (as characters), store in ∆
• (⍎¨∆)*⍴∆: evaluate each character in ∆ and raise it to the power ⍴∆
• ∆≡⍕+/: see if the input equals the string representation of the sum of these

Answer 2

GolfScript, 16 characters

~.`:s{48-s,?-}/!

Input must be given on STDIN, output is 0 or 1 indicating non-narcissistic / narcissistic number.

Explanation of the code:

~              # Evaluate the input to get a number
.              # Accumulator (initially the number itself)
`:s            # Convert number to string and assign to variable s
{              # Loop over characters of the string
  48-          # Reduce character value by 48
  s,           # Push length of input number
  ?            # Power
  -            # Subtract result from accumulator
}/
!              # Not! (i.e. iff accumulator was zero it was a narcissistic number)

Answer 3

Mathematica, 43 chars

Tr[#^Length@#&@IntegerDigits@#]==#&@Input[]

Answer 4

Perl, 38 characters

perl -lpe '$@=y///c;$s+=$_**$@for/./g;$_=$_==$s'

A pretty straightforward implementation.

Here's a slightly different version that fits in 35 characters:

perl -lpe '$@=y///c;$s+=$_**$@for/./g;$_-=$s'

This version outputs a false value if the input is narcissistic, otherwise it outputs a (Perl-accepted) true value. One might argue that this backwards version falls within the limits of the challenge description, but upon reflection I decided not to. I'm not that desperate to improve my score. Yet.

Answer 5

J, 23 chars

(".=+/@("."0^#))(1!:1)1

(1!:1)1 is keyboard input (returning a string).

". converts input to a number; "0 specifies a rank (dimension) of 0, in other words, taking each character and converting it to a number.

^ is the power function and # is the length function, thus taking each digit to the power of the length of the string (equivalently, the number of digits).

+/ is just sum, and = is comparing the sum and number.

Answer 6

Ruby, 34+5=39

With command-line flags

ruby -nlaF|

Run

p eval [$F,0]*"**#{~/$/}+"+"==#$_"

Outputs true or false.

Answer 7

R, 71 69 66 56 48

Reduced by 8 bytes thanks to @Giuseppe! The idea was to perform the integer division before the modulo operation.

i=nchar(a<-scan()):0;a==sum((a%/%10^i%%10)^i[1])

(3-year) old version with corresponding explanation:

i=nchar(a<-scan()):1;a==sum(((a%%10^i)%/%10^(i-1))^i[1])

a<-scan() takes a number (integer, real,...) as input (say 153 for the example).
i becomes a vector containing 3 to 1 (the number of characters of a being 3).
%% is vectorized so a%%10^i means a modulo 1000, 100 and 10: it therefore gives 153, 53, 3.
(a%%10^i)%/%10^(i-1) is the integer division of that vector by 100, 10, 1: therefore, 1, 5, 3.
We elevate that with the first element of i which is the number of characters (here digits) of a, i. e. 3, thus giving a vector containing 1, 125, 27 that we sum and compares to a.

Answer 8

Python 3, 56 bytes

Not very obfuscated, but a simple solution.

s = input()
print(int(s)==sum(int(c)**len(s)for c in s))

Answer 9

PHP, 80 74 66 chars

Very straightforward PHP solution:

<?for(;$i<$l=strlen($a=$argv[1]);)$s+=pow($a[$i++],$l);echo$s==$a;

It assumes error_reporting doesn't include notices, otherwise quite a few extra characters will be needed to initialize $s=0; and $i=0.

Thx @manatwork for shortening many chars.

Answer 10

Dc: 48 characters

[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p

Sample run:

bash-4.1$ dc -e '[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p' <<< '153'
1

bash-4.1$ dc -e '[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p' <<< '1634'
1

bash-4.1$ dc -e '[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p' <<< '2013'
0

Answer 11

K, 24 23

{x=+/xexp["I"$'a]@#a:$x}

Shaved 1 char with reordering

{x=+/{x xexp#x}"I"$'$x}

Answer 12

R, 53 bytes

sum(scan(t=gsub("(.)","\\1 ",x<-scan()))^nchar(x))==x

The gsub regex inserts spaces in between characters, so that the scan function will be able to read the number into a vector of digits.

Answer 13

Kona, 18

...

{x=+/(0$'u)^#u:$x}

Answer 14

Powershell, 75 63 62 60 58

Edit: Updated per @Iszi's comment (note: this counts on $x not existing)

Edit: Added @Danko's changes.

[char[]]($x=$n=read-host)|%{$x-="$_*"*$n.length+1|iex};!$x

58 56 chars

If input is limited to 10 digits (includes all int32)

($x=$n=read-host)[0..9]|%{$x-="$_*"*$n.length+1|iex};!$x

Answer 15

Python 2.x - 51

Same concept as crazedgremlin's solution for Python 3.x:

s=input();print s==sum(int(c)**len(`s`)for c in`s`)

Answer 16

C - 97 93 characters

a,b;main(c){scanf("%d",&c);b=c;for(;c;c/=10)a+=pow(c%10,(int)log10(b)+1);printf("%d",a==b);}

With indentation:

a,b;
main(c) { 
  scanf("%d",&c);
  b=c;
  for(;c;c/=10)
    a+=pow(c%10,(int)log10(b)+1);
  printf("%d",a==b);
}

Answer 17

05AB1E (legacy), 7 bytes

DSDgmOQ

Try it online!

-2 bytes thanks to @daHugLenny

Answer 18

Haskell 2010 - 76 characters

main=do x<-getLine;print$(==x)$show$sum$map((^length x).(+(-48)).fromEnum)x

Answer 19

Awk: 40 39 characters

{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1

Sample run:

bash-4.1$ awk -F '' '{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1' <<< '153'
1

bash-4.1$ awk -F '' '{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1' <<< '1634'
1

bash-4.1$ awk -F '' '{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1' <<< '2013'
0

Answer 20

Bash, 64 chars

for((a=$1;a>0;s+=(a%10)**${#1},a/=10));do :; done;echo $[s==$1]

a=$1;p=${#a};for((;a>0;a/=10));do s=$((s+(a%10)**p));done;echo $((s==$1))

Answer 21

Lua (101 chars)

Lua isn't known for being concise, but it was fun to try anyway.

for n in io.lines()do l,s=n:len(),0 for i=1,l do d=n:byte(i)s=s+(d-48)^l end print(s==tonumber(n))end

Improvements welcome.

Answer 22

Delphi - 166

uses System.SysUtils,math;var i,r,l:integer;s:string;begin r:=0;readln(s);l:=length(s);for I:=1to l do r:=round(r+power(strtoint(s[i]),l));writeln(inttostr(r)=s);end.

With indent

uses System.SysUtils,math;
var
  i,r,l:integer;
  s:string;
begin
  r:=0;
  readln(s);
  l:=length(s);
  for I:=1to l do
    r:=round(r+power(strtoint(s[i]),l));
  writeln(inttostr(r)=s);
end.

Answer 23

JavaScript - 70 58 characters

for(i in a=b=prompt())b-=Math.pow(a[i],a.length)
alert(!b)

Note:

If you're testing this in your dev console on Stack Exchange, be aware that there are a number of non-standard properties added to String.prototype that will break this solution, such as String.prototype.formatUnicorn. Please be sure to test in a clean environment, such as on about:blank.

Answer 24

Java - 84 bytes

(a,l)->{int s=0;for(byte c:a.getBytes())s+=Math.pow(c-48,l);return a.equals(""+s);};

Non-lambda version: 101 bytes:

boolean n(String a,int l){int s=0;for(byte c:a.getBytes())s+=Math.pow(c-48,l);return a.equals(""+s);}

Called like this:

interface X {
    boolean n(String a, int l);
}

static X x = (a,l)->{int s=0;for(byte c:a.getBytes())s+=Math.pow(c-48,l);return a.equals(""+s);};

public static void main(String[] args) {
    System.out.println(n("153",3));
    System.out.println(n("1634",4));
    System.out.println(n("123",3));
    System.out.println(n("654",3));
}

Returns:

true
true
false
false

Answer 25

Japt, 14 9 7 bytes

¶ì_xpZÊ

Try it online

---

Explanation

Implicit input of integer U.

ì_

Convert U to an array of digits (ì), pass it through a function and convert back to an integer after.

xpZÊ

Reduce by addition (x), raising each element to the power (p) of the length (Ê) of the array in the process.

¶

Check if the result is strictly equal to U.

Answer 26

Vyxal, 8 6 bytes

f⁰Le∑=

Try it Online!

f      # Map each digit to integer
   e   # (for each) to the power of 
 ⁰L    # Input length
    ∑  # Is sum...
     = # Equal to
       # (Implicit input)?

-2 thx to lyxal.

Answer 27

F# - 92 chars

let n=stdin.ReadLine()
n|>Seq.map(fun x->pown(int x-48)n.Length)|>Seq.sum=int n|>printf"%b"

Answer 28

Common Lisp - 116 102 characters

(defun f(m)(labels((l(n)(if(> n 0)(+(expt(mod n 10)(ceiling(log m 10)))(l(floor n 10)))0)))(= m(l m))))

Formatted:

(defun f(m)
  (labels((l(n)
            (if(> n 0)
               (+(expt(mod n 10)(ceiling(log m 10)))
                 (l(floor n 10)))
               0)))
    (=(l m)m)))

Answer 29

Smalltalk - 102 99 characters

[:n|a:=n asString collect:[:e|e digitValue]as:Array.^n=(a collect:[:each|each raisedTo:a size])sum]

At the Workspace, send value: with the number, and Print It.

Answer 30

C#, 117

using System.Linq;class A{int Main(string[] a){return a[0].Select(c=>c-'0'^a[0].Length).Sum()==int.Parse(a[0])?1:0;}}