Count the number of occurrences of each letter in string

Question

How can I count the number of occurrences in c of each letter  ignoring case  in the string  So that it would print out letter    number of occurences  I have code to count the occurences of one letter  but how can I count the occurence of each letter in the string         char     int count   0      int i         int length   strlen string        for  i   0  i  lt  20  i                  if  string i     ch                        count                         return count      output   a   1 b   0 c   2 etc

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After Accept Answer

A method that meets these specs: (IMO, the other answers do not meet all)

It is practical/efficient when char has a wide range. Example: CHAR_BIT is 16 or 32, so no use of bool Used[1 << CHAR_BIT];
Works for very long strings (use size_t rather than int).
Does not rely on ASCII. ( Use Upper[] )

Defined behavior when a char < 0. is...() functions are defined for EOF and unsigned char

static const char Upper[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
static const char Lower[] = "abcdefghijklmnopqrstuvwxyz";

void LetterOccurrences(size_t *Count, const char *s) {
  memset(Count, 0, sizeof *Count * 26);
  while (*s) {
    unsigned char ch = *s;
    if (isalpha(ch)) {
      const char *caseset = Upper;
      char *p = strchr(caseset, ch);
      if (p == NULL) {
        caseset = Lower;
        p = strchr(caseset, ch);
      }
      if (p != NULL) {
        Count[p - caseset]++;
      }
    }
  }
}

// sample usage
char *s = foo();
size_t Count[26];
LetterOccurrences(Count, s);
for (int i=0; i<26; i++)
  printf("%c : %zu\n", Upper[i], Count[i]);
}

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c code for count the occurence of each character in a string   void main           int i j  int c 26  count 0  char a    shahid      clrscr       for i 0 i lt 26 i                  count 0            for j 0 j lt strlen a  j                                       if a j   97 i                                             count                                                                              c i  count                                 for i 0 i lt 26 i                                   j 97 i            if c i   0     printf   c of  d times n  j c i                                                  getch

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include  lt stdio h gt   include  lt string h gt  void main         printf  PLEASE ENTER A STRING n        printf  GIVE ONLY ONE SPACE BETWEEN WORDS n        printf  PRESS ENETR WHEN FINISHED n         char str 100       int arr 26   0       char ch      int i       gets str       int n strlen str        for i 0 i lt n i                  ch tolower str i            if ch gt  97  amp  amp  ch lt  122                           arr ch-97                         for i 97 i lt  122 i            printf   c OCCURS  d NUMBER OF TIMES n  i arr i-97           return 0

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One simple possibility would be to make an array of 26 ints  each is a count for a letter a-z   int alphacount 26     0      0     a    1     b   etc   Then loop through the string and increment the count for each letter   for int i   0  i lt strlen mystring   i           for the whole length of the string     if isalpha mystring i            alphacount tolower mystring i  - a         make the letter lower case  if it s not                                                     then use it as an offset into the array                                                    and increment   It s a simple idea that works for A-Z  a-z  If you want to separate by capitals you just need to make the count 52 instead and subtract the correct ASCII offset

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Here is the C code with User Defined Function      C Program to count the frequency of characters in a given String      include  lt stdio h gt   include  lt string h gt   const char letters      abcdefghijklmnopqrstuvwxzy    void find frequency const char  string  int  count    int main         char string 100       int count 26      0        int i       printf  Input a string          if   fgets string  sizeof string  stdin           return 1       find frequency string  count        printf  Character Counts n         for  i   0  i  lt  26  i              printf   c t d n   letters i   count i              return 0     void find frequency const char  string  int  count        int i      for  i   0  string i       0   i              p   strchr letters  string i            if  p    NULL                count p - letters

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Have checked that many of the answered are with static array  what if suppose I have special character in the string and want a solution with dynamic concept  There can be many other possible solutions  it is one of them   here is the solutions with the Linked List    include  lt stdio h gt   include  lt string h gt   include  lt stdlib h gt   struct Node        char data       int counter      struct Node  next       void printLinkList struct Node  head        while  head    NULL             printf   n c occur  d   head- gt data  head- gt counter           head   head- gt next           int main void        char  str     count all the occurances of character in string        int i   0      char tempChar      struct Node  head   NULL       struct Node  node   NULL       struct Node  first   NULL        for i   0  i  lt  strlen str   i                  tempChar   str i            head   first           if head    NULL                        node    struct Node  malloc sizeof struct Node                node- gt data   tempChar              node- gt counter   1              node- gt next   NULL               if first    NULL                                first   node                                  else                       while  head- gt next    NULL                     if head- gt data    tempChar                                        head- gt counter   head- gt counter   1                      break                                    head   head- gt next                             if head- gt next    NULL                                if head- gt data    tempChar                                        head- gt counter   head- gt counter   1                                    else                                       node    struct Node  malloc sizeof struct Node                        node- gt data   tempChar                      node- gt counter   1                      node- gt next   NULL                      head- gt next   node                                                       printLinkList first         return 0

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This is JavaScript Code   function countWordOccurences            You can use array of words or a sentence split with space      var sentence    The quick brown fox jumped over the lazy dog          var sentenceArray     asdf    asdf    sfd    qwr    qwr        var sentenceArray   sentence split      1000        var output      var temp      for var i   0  i  lt  sentenceArray length  i              var k   1          for var j   i   1  j  lt  sentenceArray length  j                  if sentenceArray i     sentenceArray j                       k   k   1                    if k  gt  1                i   i   1              output   output         k         k                    else             output   output         k            alert sentenceArray     n    output slice 10  split      500       You can see it live -- gt  http   jsfiddle net rammipr ahq8nxpf

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include lt stdio h gt   void frequency counter char  str        int count 256     0      partial initialization     int i       for i 0 str i  i            count str i           for i 0 str i  i              if count str i                  printf   c  d  n  str i  count str i                 count str i   0                     void main         char str      The quick brown fox jumped over the lazy dog        frequency counter str

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include lt stdio h gt   include lt string h gt    define filename  somefile txt   int main         FILE  fp      int count 26     0   i  c        char ch      char alpha 27     abcdefghijklmnopqrstuwxyz       fp   fopen filename  r        if fp    NULL          printf  file not found n        while   ch   fgetc fp      EOF            c   0          while alpha c       0                  if alpha c     ch                    count c                                c                        for i   0  i lt 26 i              printf  character  c occured  d number of times n  alpha i   count i              return 0

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Like this   int counts 26   memset counts  0  sizeof counts    char  p   string  while   p        counts tolower  p    -  a          This code assumes that the string is null-terminated  and that it contains only characters a through z or A through Z  inclusive   To understand how this works  recall that after conversion tolower each letter has a code between a and z  and that the codes are consecutive  As the result  tolower  p  -  a  evaluates to a number from 0 to 25  inclusive  representing the letter s sequential number in the alphabet   This code combines    and  p to shorten the program

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You can use the following code    main         int i   0 j 0 count 26   0       char ch   97      char string 100   Hello how are you buddy         for  i   0  i  lt  100  i                  for j 0 j lt 26 j                              if  tolower string i       ch j                                         count j                                           for j 0 j lt 26 j                           printf   n c - gt   d  97 j count j                Hope this helps

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Let s assume you have a system where char is eight bit and all the characters you re trying to count are encoded using a non-negative number  In this case  you can write   const char  str    The quick brown fox jumped over the lazy dog     int counts 256      0     int i  size t len   strlen str    for  i   0  i  lt  len  i          counts  int  str i          for  i   0  i  lt  256  i          if   count i     0            printf  The  c  character has  d occurrences  n   i  counts i              Note that this will count all the characters in the string  If you are 100  absolutely positively sure that your string will have only letters  no numbers  no whitespace  no punctuation  inside  then 1  asking for  case insensitiveness  starts to make sense  2  you can reduce the number of entries to the number of characters in the English alphabet  namely 26  and you can write something like this    include  lt ctype h gt   include  lt string h gt   include  lt stdlib h gt   const char  str    TheQuickBrownFoxJumpedOverTheLazyDog    int counts 26      0     int i  size t len   strlen str    for  i   0  i  lt  len  i             Just in order that we don t shout ourselves in the foot     char c   str i       if   isalpha c   continue       counts  int  tolower c  -  a          for  i   0  i  lt  26  i          printf    c  has  2d occurrences  n   i    a   counts i

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protected void btnSave Click object sender  EventArgs e                           var FullName    stackoverflow           char   charArray   FullName ToLower   ToCharArray            Dictionary lt char  int gt  counter   new Dictionary lt char  int gt             int tempVar   0          foreach  var item in charArray                        if  counter TryGetValue item  out tempVar                                 counter item     1                            else                               counter Add item  1                                     var numberofchars               foreach  KeyValuePair lt char  int gt  item in counter                        if  counter Count  gt  0                                  Label1 Text split item                            Response Write item Value         item Key     lt br   gt                    Label1 Text item Value         item Key     lt br   gt                spnDisplay InnerText  item Value         item Key     lt br   gt

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int charset 256     0   int charcount 256     0    for  i   0  i  lt  20  i          for int c   0  c  lt  256  c                  if string i     charset c                        charcount c                         charcount will store the occurence of any character in the string

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for  int i 0 i lt word length   i              int counter 0           for  int j 0 j lt word length   j                  if word charAt i   word charAt j                counter                     inner for              JOptionPane showMessageDialog  null word charAt i    found    counter    times                 outer for

[c] Count the number of occurrences of each letter in string

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