How to remove all the occurrences of a char in c string

Question

I am using following   replace  str1 begin    str1 end     a          But this is giving compilation error

User · Answer

The algorithm std  replace works per element on a given sequence  so it replaces elements with different elements  and can not replace it with nothing   But there is no empty character  If you want to remove elements from a sequence  the following elements have to be moved  and std  replace doesn t work like this   You can try to use std  remove  together with std  erase  to achieve this   str erase std  remove str begin    str end     a    str end

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Based on other answers  here goes one more example where I removed all special chars in a given string    include  lt iostream gt   include  lt string gt   include  lt algorithm gt   std  string chars               -     int main int argc  char const  argv      std  string input  oi       std  string output   eraseSpecialChars input        return 0        std  string eraseSpecialChars std  string str    std  string newStr      newStr assign str          for int i   0  i  lt  str length    i             for int  j   0  j  lt  chars length    j                  if str at i     chars at j                    char c   str at i                   newStr erase std  remove newStr begin    newStr end    c   newStr end                                           return newStr       Input vs Output   Input ra   pha Output rapha  Input ovo  Output ovo  Input a vo Output avo  Input oi  Output oi

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Basically  replace replaces a character with another and    is not a character  What you re looking for is erase   See this question which answers the same problem  In your case    include  lt algorithm gt  str erase std  remove str begin    str end     a    str end       Or use boost if that s an option for you  like    include  lt boost algorithm string hpp gt  boost  erase all str   a      All of this is well-documented on reference websites  But if you didn t know of these functions  you could easily do this kind of things by hand   std  string output  output reserve str size        optional  avoids buffer reallocations in the loop for size t i   0  i  lt  str size      i    if str i      a   output    str i

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I guess the method std remove works but it was giving some compatibility issue with the includes so I ended up writing this little function   string removeCharsFromString const string str  char  charsToRemove         char c str length   1        terminating char     const char  p   str c str        unsigned int z 0  size   str length        unsigned int x      bool rem false       for x 0  x lt size  x                  rem   false          for  unsigned int i   0  charsToRemove i     0  i                          if  charsToRemove i     p x                                 rem   true                  break                                  if  rem    false  c z      p x              c z      0       return string c       Just use as      myString   removeCharsFromString myString   abc r      and it will remove all the occurrence of the given char list   This might also be a bit more efficient as the loop returns after the first match  so we actually do less comparison

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This code removes repetition of characters i e  if the input is aaabbcc then the output will be abc   the array must be sorted for this code to work  cin  gt  gt  s  ans    quot  quot   ans    s 0   for int i   1 i  lt  s length     i  if s i     s i-1       ans    s i   cout  lt  lt  ans  lt  lt  endl

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include  lt string gt   include  lt algorithm gt  std  string str    YourString   char chars       Y    S    str erase  std  remove str begin    str end    chars i    str end       Will remove capital Y and S from str  leaving  ourtring    Note that remove is an algorithm and needs the header  lt algorithm gt  included

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This is how I do it   std  string removeAll std  string str  char c        size t offset   0      size t size   str size         size t i   0      while  i  lt  size - offset            if  str i   offset     c                offset                       if  offset    0                str i    str i   offset                      i               str resize size - offset       return str      Basically whenever I find a given char  I advance the offset and relocate the char to the correct index  I don t know if this is correct or efficient  I m starting  yet again  at C   and i d appreciate any input on that

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string RemoveChar string str  char c        string result     for  size t i   0  i  lt  str size    i                    char currentChar   str i             if  currentChar    c                result    currentChar              return result      This is how I did it   Or you could do as Antoine mentioned      See this   question   which answers the same problem  In your case    include  lt algorithm gt  str erase std  remove str begin    str end     a    str end

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Using copy if    include  lt string gt   include  lt iostream gt   include  lt algorithm gt  int main         std  string s1    a1a2b3c4a5       char s2 256       std  copy if s1 begin    s1 end    s2     char c  return c   a          std  cout  lt  lt  s2  lt  lt  std  endl      return 0

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In case you have a predicate and or a non empty output to fill with the filtered string  I would consider   output reserve str size     output size       std  copy if str cbegin                  str cend                  std  back inserter output                 predicate      In the original question the predicate is    char c  return c     a

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70  Faster Solution than the top answer         void removeCharsFromString std  string amp  str  const char  charsToRemove                        size t charsToRemoveLen   strlen charsToRemove               std  remove if str begin    str end     charsToRemove  charsToRemoveLen  char ch  - gt  bool                                       for  int i   0  i  lt  charsToRemoveLen    i                            if  ch    charsToRemove i                               return true                                            return false

[c++] How to remove all the occurrences of a char in c++ string

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