Code Golf: Numeric equivalent of an Excel column name

StackOverflow https://stackoverflow.com/questions/2634427

  •  26-09-2019
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Question

The challenge

The shortest code by character count that will output the numeric equivalent of an Excel column string.

For example, the A column is 1, B is 2, so on and so forth. Once you hit Z, the next column becomes AA, then AB and so on.

Test cases:

A:    1
B:    2
AD:   30
ABC:  731
WTF:  16074
ROFL: 326676

Code count includes input/output (i.e full program).

Was it helpful?

Solution

Perl, 36 34 33 31 30 17 15 11 characters

$_=()=A..$_

Usage:

$ echo -n WTF | perl -ple '$_=()=A..$_'
16074

Reduced to 17 by using echo -n to avoid a chop call.

Reduced to 15 by using say instead of print.

Reduced to 11 by using -p instead of say.

Explanation: A is evaluated in string context and A..$_ builds a list starting at "A" and string-incrementing up to the input string. Perl interprets the ++ operator (and thus ..) on strings in an alphabetic context, so for example $_="AZ";$_++;print outputs BA.

=()= (aka "goatse" operator) forces an expression to be evaluated in list context, and returns the number of elements returned by that expression i.e., $scalar = () = <expr> corresponds to @list = <expr>; $scalar = @list.

OTHER TIPS

Excel, 9 chars :)

Use the right tool for the job:

=COLUMN()

=COLUMN()

J, 17 12 10 characters

26#.64-~av

Example:

26#.64-~av  'WTF'
16074

Explanation:

  • J parses from right to left.
  • av returns a list of the ascii indexes of each of the characters in its argument, so for example av'ABC' returns 65 66 67.
  • Then we subtract 64 from each element of that list with the verb 64-~.
  • Then we convert the list to base 26 using the #. verb.

Brainf*ck, 81 characters (no whitespace)

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

Explanation

,[  // get character input into p[0], enter loop if it isn't null (0)
>>>[->>+++++[-<+++++>]<+<] // take what's in p[3] and multiply by 26, storing it in p[4]
>[-<+>] // copy p[4] back to p[3]
<<++++++++[<++++++++>-]< // store 64 in p[1]
[<->-]< // subtract p[1], which is 64, from the input char to get it's alphabetical index
[>>>+<<<-] // add p[0] to p[3]
,] // get another character and repeat
>>> // move to p[3], where our final result is stored

So you'll notice I didn't actually convert the numerical value to an ascii string for printing. That would likely ruin the fun. But I did the favor of moving the pointer to the cell with the result, so at least it's useful to the machine.

Hey, what do you know, I beat C#!

Ruby 1.8.7, 53 50 46 44 24 17 characters

p ('A'..$_).count

Usage:

$ echo -n ROFL | ruby -n a.rb
326676
$ echo -n WTF | ruby -n a.rb
16074
$ echo -n A | ruby -n a.rb
1

APL

13 characters

Put the value in x:

x←'WTF'

then compute it with:

26⊥(⎕aV⍳x)-65

The only reason J beat me is because of the parentheses. I'm thinking there should be some way to rearrange it to avoid the need for them, but it's been a long day. Ideas?

(Heh, you perl programmers with your 30+ character solutions are so cute!)

Excel (not cheating), 25 chars

Supports up to XFD:

=COLUMN(INDIRECT(A1&"1"))

Installation:

  1. Put the formula in cell A2.

Usage:

  1. Enter the column string in cell A1.
  2. Read the result at cell A2.

54 chars, plus a lot of instructions

Supports ROFL also:

(A2)  =MAX(B:B)
(B2)  =IFERROR(26*B1+CODE(MID(A$1,ROW()-1,1))-64,0)

Installation:

  1. Clear the whole spreadsheet.
  2. Put the formula (A2) in cell A2.
  3. Put the formula (B2) in cell B2.
  4. Fill formula (B2) to as far down as possible.

Usage:

  1. Enter the column string in cell A1.
  2. Read the result at cell A2.

C# 156 146 118 Chars

using System.Linq;class P{static void Main(string[]a){System.Console.Write(
a[0].Aggregate(0,(t,c)=>(t+c-64)*26)/26);}}

Ungolfed:

using System.Linq;
class P
{
    static void Main(string[] a)
    {
        System.Console.Write(a[0]
            .Aggregate(0, (t, c) => (t + c - 64) * 26) / 26);
    }
}

Golfscript - 16 chars

[0]\+{31&\26*+}*


$ echo -n WTF | ./golfscript.rb excel.gs
16074
$ echo -n ROFL | ./golfscript.rb excel.gs
326676

Haskell, 50 51 56 chars

main=interact$show.foldl(\x->(26*x-64+).fromEnum)0

Usage:

~:166$ echo -n "ROFL" | ./a.out
326676
~:167$ echo -n "WTF" | ./a.out
16074

Python, 64 49 characters

s=0
for c in raw_input():s=26*s+ord(c)-64
print s

You can also replace raw_input() with input() to reduce the character count by 4, but that then requires the input to contain quotation marks around it.

And here's a subroutine that clocks in at 47 characters:

f=lambda x:len(x)and 26*f(x[:-1])+ord(x[-1])-64

k4 (kdb+), 11 characters

26/:1+.Q.A?

Explanation:

  • k4 parses left of right
  • .Q.A is defined within k4 - it is the vector "ABC...XYZ"
  • ? is the find operator - the index of the first match for items in the y arg within the x arg
  • +1 to offset the index
  • 26/: to convert to base 26

One caveat - this will only work where listed types are passed in:

  26/:1+.Q.A? "AD"
30

  26/:1+.Q.A? "WTF"
16074

but:

  26/:1+.Q.A? ,"A"
1

Powershell, 42 chars

[char[]]$args[($s=0)]|%{$s=$s*26+$_-64};$s

JavaScript 1.8: 66 characters

function a(p)Array.reduce(p,function(t,d)t*26+d.charCodeAt()-64,0)

Javascript 1.8: 72 characters

function a(p)(t=0,p.replace(/./g,function(d)t=t*26+d.charCodeAt()-64),t)

JavaScript 1.6: 83 characters

function a(p){t=0;p.split("").map(function(d){t=t*26+d.charCodeAt(0)-64});return t}

JavaScript: 95 characters

function a(p){r=0;t=1;l=p.length;for(i=0;i<l;i++){r+=(p.charCodeAt(l-1-i)-64)*t;t*=26}return r}

JavaScript: 105 characters

function a(p,i){i=i||0;l=p.length;return p?(p.charCodeAt(l-1)-64)*Math.pow(26,i)+a(p.slice(0,l-1),i+1):0}

Usage:

a("A")        // 1
a("B")        // 2
a("AD")       // 30
a("ABC")      // 731
a("WTF")      // 16074
a("ROFL")     // 326676

Scala, 30 chars

print((0/:args(0))(_*26+_-64))"

Example:

C:\>scala -e "print((0/:args(0))(_*26+_-64))" AD
30

C89, 58 characters

s;main(c){while(c=getchar()+1)s=26*s+c-65;printf("%d",s);}

The input (stdin) must contain only A-Z, no other characters (including newlines) are allowed.

Explanation of Concepts - Excelcification

Nice. I wrote my own version of this with a little more explanation a long time ago at http://aboutdev.wordpress.com/2009/12/19/excelcification-brain-teaser-code/. Although it's not quite an optimized version!

FYI. The base 26 arithmetic is called hexavigesimal and Excel's maximum column is XFD which converts to 16383 (using 0 as the first cell) which is coincidentally exactly 2^14 cells.

Can anyone guess as to why it is 2^14??

Common Lisp, 103 128 characters

(defun x(s)(reduce(lambda(x y)(+(* 26 x)y))(map 'vector(lambda(b)(-(char-code b)(char-code #\A)-1))s)))

C#, 117 111 chars

No contest compared to the likes of Perl, Ruby and APL but an improvement on the other C#/Java answers given so far.

This uses Horner's rule.

class C{static void Main(string[]a){int t=0;foreach(var c in a[0]){t=(t+c-64)*26;}System.Console.Write(t/26);}}

Perl, 34 characters

map$\=26*$\-64+ord,pop=~/./g;print

Thanks to mobrule for several suggestions.

C#, 148 chars

using System;class P{static void Main(string[]a){var r=0d;int j=0,i=a[0].
Length;while(i-->0)r+=(a[0][i]-64)*Math.Pow(26,j++);Console.WriteLine(r);}}

Ungolfed:

using System;
class P
{
    static void Main(string[] a)
    {
        var r = 0d;
        int j = 0, i = a[0].Length;
        while (i-- > 0)
            r += (a[0][i] - 64) * Math.Pow(26, j++);

        Console.WriteLine(r);
    }
}

Python - 63 chars

>>> f=lambda z: reduce(lambda x,y: 26*x+y, [ord(c)-64 for c in z])

>>> f('ROFL')

326676

Clojure:

user> (reduce #(+ (* 26 %1) %2) (map #(- (int %) 64) "AD"))
30
user> (reduce #(+ (* 26 %1) %2) (map #(- (int %) 64) "ROFL"))
326676

51 characters, plus the number of characters in the input string.

C:

int r=0;
while(*c)r=r*26+*c++-64;

String is stored in 'c', value is in 'r'.

Ruby 1.9, 21 characters

p'A'.upto(gets).count

Tests:

$ echo -n A| ruby x.rb
1
$ echo -n WTF| ruby x.rb
16074
$ echo -n ROFL| ruby x.rb
326676

Common Lisp, 86 characters.

(defun z(s)(let((a 0))(map nil(lambda(v)(setf a(+(* 26 a)(digit-char-p v 36)-9)))s)a))

Java: 112 124 characters

class C{public static void main(String[]a){int r=0;for(int b:a[0].getBytes())r=26*r+b-64;System.out.print(r);}}

Common Lisp, 81 characters

(defun y(s)(reduce(lambda(x y)(+(* 26 x)(-(char-code y)64)))s :initial-value 0))

Funny that as a new user I can post my own answer but not comment on someone else's. Oh well, apologies if I'm doing this wrong!

MATLAB: 24 characters

polyval(input('')-64,26)

Usage:

>> polyval(input('')-64,26)
(after pressing enter) 'WTF'

ans =

       16074

Note: You can get it down to 16 characters if you pre-store the string in x, but I kind of thought it was cheating:

>> x = 'WTF'

x =

WTF

>> polyval(x-64,26)

ans =

       16074

PHP - 73 Chars

$n=$argv[1];$s=$i=0;while($i<strlen($n))$s=$s*26+ord($n[$i++])-64;echo$s;

Usage:

php -r '$n=$argv[1];$s=$i=0;while($i<strlen($n))$s=$s*26+ord($n[$i++])-64;echo$s;' AA

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