# Test a number for narcissism

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

• Is it ok if I output True if it's such a number, but anything else (in this case the number itself) if not? Jan 6 '17 at 21:51

## 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
• what did i just read Feb 18 '14 at 20:13
• @LagWagon God's language Jul 8 '14 at 8:00

### 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)

• I did a double-take on  ~.  but it seems impossible to improve. Nice one. Nov 20 '13 at 17:28

# Mathematica, 43 chars

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


## 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;$s+=$_**$@for/./g;$_-=$s'  This version outputs a false value if the input is narcissistic, otherwise it outputs a (Perl-accepted) true value. One might argue that this backwards version falls within the limits of the challenge description, but upon reflection I decided not to. I'm not that desperate to improve my score. Yet. • “Error checking for text strings or other invalid inputs is not required.” – So why not suppose the input will be valid number, without trailing newline? echo -n 153 | perl -pe '…' will work without -l. Nov 14 '13 at 12:26 • I think so long as you define what your true and false outputs are, it should be legal Nov 14 '13 at 16:48 • Strictly speaking, the wording of the challenge text does leave a bit of ambiguity as to what True/False or 0/1 should mean, so I'll let this one pass. A different script of equal length that returns true for narcissistic values would have the advantage, though. – Iszi Nov 14 '13 at 20:47 • Same idea but shorter: perl -pe'map$s+=$_**@y,@y=/./g;$_=$_==$s' Jun 19 '16 at 7:48

# 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.

• "Your code must take input from the user and output True or False depending upon whether the given number is a Narcissistic Number." (emphasis mine) Nov 14 '13 at 4:45
• @JanDvorak My bad -- added keyboard input. Nov 14 '13 at 6:08

# Ruby, 34+5=39

With command-line flags

ruby -nlaF|


Run

p eval [$F,0]*"**#{~/$/}+"+"==#$_"  Outputs true or false. • This may be the most Ruby flags I've ever seen in a legitimate code golf :P – Doorknob Nov 21 '13 at 21:24 ## R, 71696656 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. • Does the integer division always round down? Otherwise, you could run into problems with e.g. 370 (a narcissistic number) turning into 4,7,0 (which would return false) or 270 (non-narcissistic) turning into 3,7,0 (returning true). – Iszi Nov 14 '13 at 20:40 • Integer division doesn't round... The integer division of 370 by 100 is 3 with the remainder of 70 and not 3.70. Nov 15 '13 at 7:40 • 48 bytes...somebody bumped this to the homepage! Sep 1 '17 at 19:55 # 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))  • The [ and ] are unnecessary, and you can drop the space in front of for too, so: sum(int(c)**len(s)for c in s) Nov 14 '13 at 7:12 • That's awesome! Thanks for the tip. Nov 14 '13 at 12:05 • You can save two characters by removing the spaces in s = input() and another one by moving this to 2.7 where print isn't a function. – Ben Nov 16 '13 at 17:31 • Good point, edited. Nov 17 '13 at 5:32 • I think you should point out that adding braces to print (hence one character more) would make this a valid Python 2.x and Python 3.x solution. Nov 18 '13 at 18:24 ## PHP, 8074 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 $i=0. Thx @manatwork for shortening many chars. • Don't assign$a and $l in separate statements. <?for($i=0;$i<$l=strlen($a=$argv[1]);$i++){$s+=pow($a[$i],$l);}echo$s==$a; is shorter. Nov 14 '13 at 14:58 • As you already have a statement which generate a notice, just add another: remove the loop control variable initialization. Incrementing the loop control variable also not need to be a standalone statement. And the braces are definitely not needed: <?for(;$i<$l=strlen($a=$argv[1]);)$s+=pow($a[$i++],$l);echo$s==$a;. Nov 14 '13 at 15:09 • @manatwork: Thank you for the warm welcome to codegolf :) Nov 14 '13 at 15:13 • Can be golfed to this for(;$i<$l=strlen($a=$argn);)$s+=$a[$i++]**$l;echo$s==$a; May 17 '17 at 16:51 # Dc: 48 characters [1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p  Sample run: bash-4.1$ 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

• Never actually used dc, save for frantic typos in attempt to write cd Jan 5 '18 at 1:54

# K, 24 23

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


Shaved 1 char with reordering

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


# 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.

• +1 i would have never thought of doing that, it's brilliant. Nov 15 '13 at 16:26

# Kona, 18

...

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


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  • I was wondering if someone was going to do PowerShell before I did. – Iszi Nov 14 '13 at 20:55 • Save 12 characters by adding another variable $x and using += to do your summing instead of measure -sum then test $x-eq$n.
– Iszi
Nov 14 '13 at 21:03
• 61 chars: ($x=$n=read-host)-split''|%{$x-=[math]::pow($_,$n.length)};!$x Nov 15 '13 at 9:04
• @DankoDurbić, Nice! Type coercion often comes in handy with PoSh code golfing. I only get 62 though when I run '($x=$n=read-host)-split""|%{$x-=[math]::pow($_,$n.length)};!$x'.length Nov 15 '13 at 15:06
• @Rynant Good point. I ran your length check in PowerShell and came up with 62 as well. When running a length check similarly against the actual script, it comes up 61. This is probably because of how PowerShell handles the '' which you replaced with ''. I took the original script into Excel to double-check with =LEN("($x=$n=read-host)-split''|%{$x-=[math]::pow($_,$n.length)};!$x") and got 62 also. Of course, we could always count it manually - but who really does that?
– Iszi
Nov 15 '13 at 15:22

## 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 ins)


## 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);
}

• You don't have to define int for global variables. Jan 10 '14 at 15:49
• Woah. You're reading the input into argc. Jan 6 '17 at 14:16
• Also, shouldn't having to do -lm at compile-time count +1 byte? Jan 6 '17 at 14:21
• @Blacksilver the -lm flag is not required for C89 compilers.
– Josh
Jan 9 '17 at 14:55
• Aha. Learn a new thing every day. Jan 9 '17 at 14:59

# 05AB1E (legacy), 7 bytes (Non-competing)

DSDgmOQ


Try it online!

-2 bytes thanks to @daHugLenny

• You can replace §1ô with S Nov 8 '16 at 15:45

# Haskell 2010 - 76 characters

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

• You shouldn't post the number of ms to run the code, but the number of chars you used. ;) Nov 15 '13 at 4:02

{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  # 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))

• You are using variable p in a single place, so no need for it. You can move the initialization of variable a into the for to spare its separate ;: for((a=$1;a>0;a/=10));do s=$[s+(a%10)**${#1}];done;echo$[s==$1]. Nov 15 '13 at 11:08 • By moving the evaluation into the for one more character can be shortened: for((a=$1;a>0;s+=(a%10)**${#1},a/=10));do :; done;echo$[s==\$1]. Nov 15 '13 at 11:16
• Oh, curious! I tried something like that, but it didn't work. Curious what went wrong. Nov 16 '13 at 1:53

## 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.

• As it is not required that your program can handle and process a list of numbers, I would not use bytes to implement that functionality. Replacing the loop for n in io.lines()do [...]end with n=io.read() saves some bytes (TIO). Sep 1 '17 at 19:55

# 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;
l:=length(s);
for I:=1to l do
r:=round(r+power(strtoint(s[i]),l));
writeln(inttostr(r)=s);
end.


## JavaScript - 70 58 characters

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


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.

• I count 70 characters there. Nov 15 '13 at 16:10
• @manatwork, whoops, forgot to count the newline. Nov 15 '13 at 19:10
• Great trick that decrementation! Nov 16 '13 at 13:12
• it always returns true for me, regardless of input
– koko
Jul 8 '14 at 9:27
• @koko, I've added a note to explain why you're receiving incorrect results. Nov 8 '16 at 15:00

# 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


# Japt, 149 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.

• I think ¥U¬®n pUlÃx would work for 11 bytes ;) May 18 '17 at 17:39

# 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.

## F# - 92 chars

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


# 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)))


# 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.

# 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;}}
`