Character Frequency in a String

Question

Given a string of printable ASCII, output the frequency of each character in that string.

The Challenge

• Input is given as a string of printable ASCII characters (decimal [32-126] inclusive).
• Output the frequency of each character, in ASCII order.
• The output must have a format similar to [character][separator][count]. Provided that there is a single, non-newline separating string between the character and its frequency, it is a valid output.
• Output can be a single string, multiple strings, list of 2-tuples, array of tuples, etc.
• Input and output can be given using any convenient method.
• Standard loopholes are forbidden.
• This is code-golf, so shortest in bytes wins.

Sample I/O

abcd
//outputs
a: 1
b: 1
c: 1
d: 1

Over 9001!
//outputs
  [ 1
! [ 1
0 [ 2
1 [ 1
9 [ 1
O [ 1
e [ 1
r [ 1
v [ 1

--<-<<+[+[<+>--->->->-<<<]>]<<--.<++++++.<<-..<<.<+.>>.>>.<<<.+++.>>.>>-.<<<+.
//outputs (as 2-tuples)
(+,14),(-,13),(.,13),(<,21),(>,13),([,2),(],2)

Su3OH39IguWH
//outputs (as 2d array)
[[3,2],[9,1],[H,2],[I,1],[O,1],[S,1],[W,1],[g,1],[u,2]]

Answer 1

Python 3, 50, 43, 41 bytes

lambda s:{c:s.count(c)for c in sorted(s)}

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Answer 2

Ohm v2, 2 bytes

SÖ

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      implicit input
S     sort string
 Ö    run-length encoding
      implicitly print

Answer 3

Python 3, 41 bytes

lambda s:sorted({*zip(s,map(s.count,s))})

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Answer 4

J, 13 bytes

({.;#)/.~@/:~

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• @/:~ sort the input and...
• /.~ partition it into groups of like items. Apply the following to each group...
• ({.;#) take the first element {. and link it ; to the number of items in the group #

Answer 5

Brachylog, 2 bytes

ọo

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ọ     Occurrences,
 o    sorted.

It's essentially the same as using an RLE builtin with the sorting requirement, but if the output could be in any order it would just be ọ.

Answer 6

APL (Dyalog Extended), 5 bytes^SBCS

Anonymous tacit prefix function, returning a two-column table, which by default prints with space as separator between character and count, and line break after each entry.

,∘≢⌸∧

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, character followed

∘ by

≢ its tally

⌸ for each unique character

∧ in ascending order

Answer 7

Haskell, 52 49 bytes

-3 bytes thanks to cole!

import Data.List
map((,).nub<*>length).group.sort

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I know this is too long (especially that import), but I'm new at Haskell golfing and hoping to get better! Outputs as a list of tuples of (character, count) (note the character is String, not a Char).

Answer 8

Perl 6, 15 bytes

*.comb.Bag.sort

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Anonymous code block that takes a string and returns a list of pairs, where the key is the character and the value is the number of occurrences.

Explanation:

*.comb           # Decompose into characters
      .Bag       # Group into unordered bag of character => occurrences
          .sort  # Sort by character

Answer 9

CJam, 8 4 bytes

$e`p

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-3 bytes thanks to Jonah, and -1 byte from rule interpretation.

A perfect challenge for CJam. I had hoped that the RLE encode operator would output [char, count], but the order was reversed. Otherwise it would have been a 5-byter. After Jonah's comment, I switched the order of the output. I'm not sure if the first read should be counted, since the standard rules permit input to be on the stack at the start of the program. If that's the case, this answer is one byte shorter. From this meta discussion, I concluded that the read could be placed in the header. Otherwise I could modify the script to be a function without changing the byte count.

Explanation

 $       sort string
  e`     RLE-encode (transforms "aabc" to [[2, "a"], [1, "b"], [1, "c"]]
    p    print

Open question: would something like this be allowed if transforming the answer to a function, or should the brackets be included in the byte count?

Answer 10

Bash, ^{27 22} 20 bytes

fold -1|sort|uniq -c

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-5 bytes thanks to Neil

-2 bytes thanks to Digital Trauma

Answer 11

Jelly, 6 3 bytes

ṢŒr

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A monadic link taking the string as its argument. Returns a list of lists, each one containing the character and count. The footer formats this as a grid.

Answer 12

Pyth, 3 bytes

r8S

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Simply run-length encodes (r8) the sorted (S) input. Output is a list of tuples of [frequency, character].

Answer 13

T-SQL 2008 query, 130 bytes

DECLARE @ varchar(2000)='kabcdda'

SELECT w,sum(1)FROM(SELECT
substring(@,number+1,1)FROM
spt_values WHERE type='P'and
number<len(@))x(w)GROUP BY w
ORDER BY ascii(w)

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Answer 14

PHP, 57 bytes

foreach(count_chars($argn,1)as$a=>$b)echo chr($a)," $b
";

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Input via STDIN, run with php -F:

$ echo Su3OH39IguWH|php -F cc.php
3 2
9 1
H 2
I 1
O 1
S 1
W 1
g 1
u 2

Fun fact: this challenge is basically the Example 1 on the PHP docs for count_chars().

Answer 15

JavaScript, 58 bytes

s=>[...s].sort().flatMap(c=>c>p?[p=[c,1]]:p[1]++&&[],p=[])

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Thanks Shaggy, -1 byte.

---

Retina, 18 bytes

O`.
(.)\1*
$1,$.&¶

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I don't speak Retina. I just translated above JavaScript answer to Retina with some searching.

Thanks to Cows quack, -3 bytes.

Answer 16

PowerShell, 27 22 21 19 bytes

$args[0]|sort|group

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Exactly what it says on the tin. Takes input $args[0] via splatting (manifests on TIO as a [char[]]), sorts it, then group-object it into a grouping.

-8 bytes thanks to mazzy

Answer 17

C (gcc), 94 91 bytes

Thanks to Ourous and ceilingcat for their suggestions.

To get the non-newline separator, I'm making use of the fact that negative numbers get a "-" for free! :-)

f(char*s){char c[255]={},i=31;for(;*s;)c[*s++]--;for(;++i>0;)c[i]&&printf("%c%d ",i,c[i]);}

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Answer 18

Wolfram Language (Mathematica), 34 bytes

KeySortBy[ToCharacterCode]@*Counts

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Returns an association.

---

SortBy[ToCharacterCode@@#&]@*Tally

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Returns a list.

Answer 19

C# (Visual C# Interactive Compiler), 63 61 bytes

s=>s.OrderBy(c=>c).GroupBy(c=>c).Select(g=>(g.Key,g.Count()))

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Thanks to Expired Data for pointing me towards the C# Interactive Compiler and for showing me the power of dynamics.

Answer 20

K4, 9 bytes

Solution:

#:'=x@<x:

Example:

q)k)#:'=x@<x:"Over 9001!"
 | 1
!| 1
0| 2
1| 1
9| 1
O| 1
e| 1
r| 1
v| 1

Explanation:

#:'=x@<x: / the solution
       x: / store input as x
      <   / indices to sort ascending
    x@    / apply (@) to x
   =      / group same values
#:'       / count (#:) each (')

Answer 21

brainfuck, 128 114 bytes

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

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How it works:

-                                          sets cell 0 to 255, which is used to move back to cell 2 later on
>>                                         moves to cell 2
,[                                         we load our first input and loop until there are no more characters to load
[-[>>+<<-]>>]                              keeps moving forward skipping every other cell until it has moved forward the ASCII value of the most recently loaded character  
>+<                                        adds one to the next cell for the purpose of later looking at to see how many of that character was entered
+[-<<+]->>                                 goes back to cell 2
,]                                         loads in next character and repeats process if there are remaining characters

+[+>[                                      checks IF the next cell has a value other than 0
<--.                                       then, if true, it prints the ASCII value of the previous cells contents
++<<+++++++[>++++++++<-]>++.               then print ":"
[-]++++++[>>++++++++<<-]>>.                then print the number value of the contents of the current cell
[-].]                                      then print a null character and leaves the if statement
<[>>+<<-]>>]                               continues the same process skipping every other cell, until it repeats 255 times

Thanks to Jo King, -14 bytes.

This is my second brainfuck program, first being hello world, and first time golfing, so please let me know what I can do to improve my program and answer!

Answer 22

APL(NARS), 26 chars, 52 bytes

{m,¨+/¨{w=⍵}¨m←k[⍋k←∪w←⍵]}

test:

  ⎕fmt{m,¨+/¨{w=⍵}¨m←k[⍋k←∪w←⍵]}'is, this good or not?'
┌12─────────────────────────────────────────────────────────────────────────────────┐
│┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐ ┌2───┐│
││   4│ │ , 1│ │ ? 1│ │ d 1│ │ g 1│ │ h 1│ │ i 2│ │ n 1│ │ o 4│ │ r 1│ │ s 2│ │ t 2││
│└+───┘ └+───┘ └+───┘ └+───┘ └+───┘ └+───┘ └+───┘ └+───┘ └+───┘ └+───┘ └+───┘ └+───┘2
└∊──────────────────────────────────────────────────────────────────────────────────┘

  {m,¨+/¨{w=⍵}¨m←k[⍋k←∪w←⍵]}
                     k←∪w←⍵     copy the argument in w, k is the argument that has unique elements
               m←k[⍋       ]    copy k order, in m, (so m is argument unique ordered)
         {w=⍵}¨m                see each element of m in w, so each element of m generate a len(w) bit list 
      +/¨                       sum each bit list above obtain the number of element of m in w
   m,¨                          make couples

Answer 23

Clean, 60 bytes

import StdEnv
$s=sort[(c,sum[1\\k<-s|k==c])\\c<-removeDup s]

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Defines the function $ :: [Char] -> [(Char, Int)] giving the result as a list of 2-Tuples.
Uses the element-wise behavior of < and thus sort on Tuples to ensure codepoint ordering.

Answer 24

sfk, 124 87 84 bytes

xed -i
+chars
+count -same -case
+xed "_?????*x*[white]?_[parts 6,3,1]_"
+sort -case

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Gives output in the form [character]x[count] with count padded to 5 digits.

Answer 25

JavaScript, 57 bytes

Outputs a 2D-Array. Had to implement a quick & dirty fix for the sorting so I'll need to come back to try to golf that.

s=>[...s].map(o=x=>o[x]=-~o[x])&&Object.entries(o).sort()

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Answer 26

Charcoal, 13 bytes

ＥΦγ№θι⁺⁺ι №θι

Try it online! Link is to verbose version of code. Explanation:

  γ             Printable ASCII
 Φ              Filtered where non-zero
   №            Count of
     ι          Current character in
    θ           Input string
Ｅ               Map over filtered characters
        ι       Current character
       ⁺        Plus a space
      ⁺         Plus
          №     Count of
            ι   Current character in
           θ    Input string
                Implicitly output on separate lines

Answer 27

Japt, 10 8 bytes

ü
mÎíUmÊ

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ü\nmÎíUmÊ     :Implicit input of string U
ü             :Split, sort and partition by value
 \n           :Reassign to U
   m          :Map
    Î         :  First element
     í        :Interleave with
      UmÊ     :  Map lengths of U

Answer 28

Kotlin, 75 bytes

fun String.c()=toCharArray().sorted().map{Pair(it,count{s->it==s})}.toSet()

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Answer 29

Java (JDK), 82 bytes

s->s.stream().sorted().distinct().map(c->c+" "+s.stream().filter(x->c==x).count())

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Answer 30

Japt, 7 bytes

¬ü ®âZl

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Answer 31

Haskell, 46 bytes

f x=[(c,sum[1|d<-x,d==c])|c<-[' '..],elem c x]

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Answer 32

Ruby -n, 43 bytes

p$_.chars.uniq.sort.map{|c|[c,$_.count(c)]}

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Answer 33

Kotlin, 53 bytes

Returns a Map<Char, Int> associating characters to frequencies. The map keys are sorted in ASCII order (it's a java.util.SortedMap underneath.)

{s->s.associateWith{c->s.count{it==c}}.toSortedMap()}

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Answer 34

05AB1E, 8 6 bytes

SêDŠ¢ø

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Answer 35

R (in C locale), 32 bytes

function(s)table(strsplit(s,''))

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strsplit the input character string by the empty string to separate its characters then table builds a contingency table of the unique character counts.

Answer 36

JavaScript, 55  48  62 57 bytes

a=>[...a].sort().map(c=>o.set(c,-~o.get(c)),o=new Map)&&o

output is a Map

contrary to Objects, Map remember the order in which values where sets

let input = document.getElementById("input")
let run = document.getElementById("run")
let output = document.getElementById("output")

run.onclick = () => {
  output.innerHTML = ""
  func(input.value).forEach((val, key) => output.innerHTML += `'${key}' => ${val}<br>`)
}

let func = a=>[...a].sort().map(c=>o.set(c,-~o.get(c)),o=new Map)&&o

<input id="input"/>
<button id="run">run</button>
<p id="output"></p>

Thanks to Shaggy and Einacio for pointing my flaws

-5 bytes thanks to Shaggy

Answer 37

Forth (gforth), 134 bytes

: f here 128 allot dup 128 erase -rot 0 do 2dup i + c@ + 1 swap +! loop drop
128 0 do dup i + c@ ?dup if i emit ." : ". cr then loop ;

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Limitation: won't work if any character occurs more than 256 times in a single string (to fix this requires an extra ~25 bytes)

Explanation

• Allocate an area of memory 128 bytes (cells if needed) wide to use as an array/dictionary
• Zero out all bytes/cells in that area
• Loop through string, for each character
  • Add ascii value to array starting address, then increment value at that address by 1
• When finished, loop through array/dictionary and output all chars/values that have a value other than 0

Code Explanation

: f                     \ start new word definition
  here 128 allot        \ allocate 128 bytes to use as an array
  dup 128 erase         \ fill array with zeros
  -rot                  \ stick array address behind string address
  0 do                  \ start counted loop from 0 to string-length - 1
    2dup                \ duplicate array and string address
    i + c@              \ get ascii value of next character in string
    + 1 swap +1         \ add to array address, then add 1 to the value in that array position
  loop                  \ end the loop
  drop                  \ drop the string address [no longer needed]
  128 0 do              \ start a counted loop from 0 to 127
    dup i + c@          \ get value at next array position
    ?dup                \ duplicate if >0
    if                  \ start an if block (if >0)
      i emit            \ output the character
      ." : ".           \ output ": " followed by the number of that char in the string
      cr                \ output a newline
    then                \ end the if block
  loop                  \ end the loop
;                       \ end the word definition

Answer 38

Red, 92 bytes

func[s][parse/case sort/case s[any[copy k[copy t skip thru any t](print[t length? to""k])]]]

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Answer 39

Perl 5 (-nF -M5.01 -MList::Util=uniq), 49 41 bytes

41 bytes : for$a(uniq sort@F){say"$a ",eval"y/$a//"} doesn't work if input contains a slash. Otherwise, 36 bytes : for$a(uniq sort@F){say"$a "./\Q$a/g} doesn't work because of //g in scalar context.

for$a(uniq sort@F){say"$a ".(()=/\Q$a/g)}

TIO

first answer

Answer 40

Scala, 64 62 bytes

(x:String)=>x.groupBy(identity).mapValues(_.size).toSeq.sorted

Answer 41

C++ (gcc), 85 bytes

#include<map>
auto f(std::string s){std::map<char,int>m;for(int c:s)m[c]++;return m;}

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This solution makes use of several nice features of std::map:

1. It has a sorted iterator, with default lexicographic ordering.
2. The []-operator default initializes members, in case of int it zeroes it.

Also, C++17 allows for golfing using auto and range-for loop.

Answer 42

SNOBOL4 (CSNOBOL4), 120 bytes

	A =&ALPHABET
	I =INPUT
S	O =0
	A LEN(1) . X REM . A	:F(END)
R	I X =	:F(O)
	O =O + 1	:(R)
O	OUTPUT =GT(O) X 0 O	:(S)
END

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	A =&ALPHABET			;* alias for &ALPHABET (256 characters in ascending order)
	I =INPUT			;* read input
S	O =0				;* set counter to 0
	A LEN(1) . X REM . A	:F(END)	;* set X to first letter of A
					;* setting the REMainder to A
					;* and going to END if no letters remain
R	I X =	:F(O)			;* remove the first occurrence of X from I
					;* and output if none are left
	O =O + 1	:(R)		;* increment the counter, going to R
O	OUTPUT =GT(O) X 0 O	:(S)	;* if O > 0,
					;* output X 0 and O in that order
					;* then GOTO S
END

Answer 43

JavaScript (Node.js), 56 bytes

s=>[...s].sort().reduce((a,b)=>(a[b]=(a[b]||0)+1)&&a,{})

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