Removing leading and trailing spaces from a string

Question

How to remove spaces from a string object in C    For example  how to remove leading and trailing spaces from the below string object       Original string            This is a sample string                        Desired string   This is a sample string    The string class  as far as I know  doesn t provide any methods to remove leading and trailing spaces     To add to the problem  how to extend this formatting to process extra spaces between words of the string  For example      Original string             This       is         a sample   string          Desired string    This is a sample string      Using the string methods mentioned in the solution  I can think of doing these operations in two steps    Remove leading and trailing spaces  Use find first of  find last of  find first not of  find last not of and substr  repeatedly at word boundaries to get desired formatting

User · Answer

Why complicate  std  string removeSpaces std  string x       if x 0            x erase 0  1   return removeSpaces x         if x x length   - 1            x erase x length   - 1  x length     return removeSpaces x         else return x     This works even if boost was to fail  no regex  no weird stuff nor libraries  EDIT  Fix for M M  s comment

User · Answer

Boost string trim algorithm   include  lt boost algorithm string trim hpp gt          std  string msg       some text  with spaces     boost  algorithm  trim msg

User · Answer

C  17 introduced std  basic string view  a class template that refers to a constant contiguous sequence of char-like objects  i e  a view of the string  Apart from having a very similar interface to std  basic string  it has two additional functions  remove prefix    which shrinks the view by moving its start forward  and remove suffix    which shrinks the view by moving its end backward  These can be used to trim leading and trailing space   include  lt string view gt   include  lt string gt   std  string view ltrim std  string view str        const auto pos str find first not of  quot   t quot         str remove prefix pos       return str     std  string view rtrim std  string view str        const auto pos str find last not of  quot   t quot         str remove suffix str length   - pos - 1       return str     std  string view trim std  string view str        str   ltrim str       str   rtrim str       return str     int main         std  string str    quot    hello world    quot       auto sv1  ltrim str          quot hello world    quot      auto sv2  rtrim str          quot    hello world quot      auto sv3  trim str           quot hello world quot         If you want  you can create std  string objects from std  string view objects     auto s1  sv1        auto s2  sv2        auto s3  sv3       Note  the std  string view is a non-owning reference  so it s only valid as long as the original string still exists

User · Answer

No boost  no regex  just the string library  It s that simple   string trim const string s       removes whitespace characters from beginnig and end of string s     const int l    int s length        int a 0  b l-1      char c      while a lt l  amp  amp    c s at a         c    t   c    n   c    v   c    f   c    r   c    0    a        while b gt a  amp  amp    c s at b         c    t   c    n   c    v   c    f   c    r   c    0    b--      return s substr a  1 b-a

User · Answer

Example for trimming leading and trailing spaces     std  string aString      This is a string to be trimmed       auto start   aString find first not of       auto end   aString find last not of       std  string trimmedString  trimmedString   aString substr start   end - start    1     OR   trimmedSring   aString substr aString find first not of        aString find last not of      - aString find first not of         1

User · Answer

void removeSpaces string amp  str           remove multiple spaces        int k 0      for  int j 0  j lt str size      j                    if    str j              str j          amp  amp  str j 1                                              str  k    str  j                         k                           str resize k           remove space at the end           if  str  k-1                      str erase str end  -1          remove space at the begin        if  str  0                      str erase str begin

User · Answer

Easy removing leading  trailing and extra spaces from a std  string in one line  value   std  regex replace value  std  regex                     1      removing only leading spaces  value erase value begin    std  find if value begin    value end    std  bind1st std  not equal to lt char gt               or  value   std  regex replace value  std  regex                removing only trailing spaces  value erase std  find if value rbegin    value rend    std  bind1st std  not equal to lt char gt           base    value end       or  value   std  regex replace value  std  regex                removing only extra spaces  value   regex replace value  std  regex

User · Answer

void TrimWhitespaces std  wstring amp  str        if  str empty            return       const std  wstring amp  whitespace   L   t       std  wstring  size type strBegin   str find first not of whitespace       std  wstring  size type strEnd   str find last not of whitespace        if  strBegin    std  wstring  npos    strEnd    std  wstring  npos                strBegin    std  wstring  npos   0   strBegin          strEnd    std  wstring  npos   str size     0           const auto strRange   strEnd - strBegin   1          str substr strBegin  strRange  swap str             else if  str 0            str 0       t        handles non-empty spaces-only or tabs-only               str   L             void TrimWhitespacesTest         std  wstring EmptyStr   L        std  wstring SpacesOnlyStr   L            std  wstring TabsOnlyStr   L                   std  wstring RightSpacesStr   L 12345            std  wstring LeftSpacesStr   L      12345       std  wstring NoSpacesStr   L 12345        TrimWhitespaces EmptyStr       TrimWhitespaces SpacesOnlyStr       TrimWhitespaces TabsOnlyStr       TrimWhitespaces RightSpacesStr       TrimWhitespaces LeftSpacesStr       TrimWhitespaces NoSpacesStr        assert EmptyStr    L         assert SpacesOnlyStr    L         assert TabsOnlyStr    L         assert RightSpacesStr    L 12345        assert LeftSpacesStr    L 12345        assert NoSpacesStr    L 12345

User · Answer

Example for trim leading and trailing spaces following jon-hanson s suggestion to use boost  only removes trailing and pending spaces     include  lt boost algorithm string trim hpp gt   std  string str       t e s t        boost  algorithm  trim   str      Results in  t e s t   There is also    trim left results in  t e s t     trim right results in     t e s t

User · Answer

string trim const string  amp  sStr        int nSize   sStr size        int nSPos   0  nEPos   1  i      for i   0  i lt  nSize    i            if   isspace  sStr i                    nSPos   i               break                      for i   nSize -1   i  gt   0   --i            if   isspace  sStr i                    nEPos   i              break                      return string sStr  nSPos  nEPos - nSPos   1

User · Answer

This is called trimming  If you can use Boost  I d recommend it   Otherwise  use find first not of to get the index of the first non-whitespace character  then find last not of to get the index from the end that isn t whitespace  With these  use substr to get the sub-string with no surrounding whitespace   In response to your edit  I don t know the term but I d guess something along the lines of  reduce   so that s what I called it      Note  I ve changed the white-space to be a parameter  for flexibility    include  lt iostream gt   include  lt string gt   std  string trim const std  string amp  str                   const std  string amp  whitespace      t         const auto strBegin   str find first not of whitespace       if  strBegin    std  string  npos          return        no content      const auto strEnd   str find last not of whitespace       const auto strRange   strEnd - strBegin   1       return str substr strBegin  strRange      std  string reduce const std  string amp  str                     const std  string amp  fill                           const std  string amp  whitespace      t            trim first     auto result   trim str  whitespace           replace sub ranges     auto beginSpace   result find first of whitespace       while  beginSpace    std  string  npos                const auto endSpace   result find first not of whitespace  beginSpace           const auto range   endSpace - beginSpace           result replace beginSpace  range  fill            const auto newStart   beginSpace   fill length            beginSpace   result find first of whitespace  newStart              return result     int main void        const std  string foo        too much t    tspace t t t         const std  string bar    one ntwo        std  cout  lt  lt       lt  lt  trim foo   lt  lt       lt  lt  std  endl      std  cout  lt  lt       lt  lt  reduce foo   lt  lt       lt  lt  std  endl      std  cout  lt  lt       lt  lt  reduce foo   -    lt  lt       lt  lt  std  endl       std  cout  lt  lt       lt  lt  trim bar   lt  lt       lt  lt  std  endl      Result    too much               space     too much space     too-much-space     one   two

User · Answer

strip a string  remove leading and trailing spaces void strip const string amp  in  string amp  out        string  const iterator b   in begin    e   in end            skipping leading spaces     while  isSpace  b              b             if  b    e              skipping trailing spaces         while  isSpace   e-1                 --e                       out assign b  e       In the above code  the isSpace   function is a boolean function that tells whether a character is a white space  you can implement this function to reflect your needs  or just call the isspace   from  ctype h  if you want

User · Answer

I ve tested this  it all works  So this method processInput will just ask the user to type something in  it will return a string that has no extra spaces internally  nor extra spaces at the begining or the end  Hope this helps   also put a heap of commenting in to make it simple to understand    you can see how to implement it in the main   at the bottom   include  lt string gt   include  lt iostream gt   string processInput       char inputChar 256     string output         int outputLength   0    bool space   false       user inputs a string   well a char array   cin getline inputChar 256     output   inputChar         string outputToLower            put characters to lower and reduce spaces   for int i   0  i  lt  output length    i            if it s caps put it to lowercase     output i    tolower output i           make sure we do not include tabs or line returns or weird symbol for null entry array thingy     if  output i       t   amp  amp  output i       n   amp  amp  output i                   if  space               if the previous space was a space but this one is not  then space now is false and add char         if  output i                      space   false               add the char           outputToLower  output i                     else              if space is false  make it true if the char is a space         if  output i                      space   true                       add the char         outputToLower  output i                          trim leading and tailing space   string trimmedOutput         for int i   0  i  lt  outputToLower length    i            if it s the last character and it s not a space  then add it        if it s the first character and it s not a space  then add it        if it s not the first or the last then add it     if  i    outputToLower length   - 1  amp  amp  outputToLower i                   i    0  amp  amp  outputToLower i                   i  gt  0  amp  amp  i  lt  outputToLower length   - 1          trimmedOutput    outputToLower i                   return   output   trimmedOutput    return output     int main       cout  lt  lt   Username       string userName   processInput      cout  lt  lt    nModified Input      lt  lt  userName  lt  lt  endl

User · Answer

My Solution for this problem not using any STL methods but only C   string s own methods is as following   void processString string  amp s        if   s empty     return         delete leading and trailing spaces of the input string     int notSpaceStartPos   0  notSpaceEndPos   s length   - 1      while   s notSpaceStartPos             notSpaceStartPos      while   s notSpaceEndPos           --notSpaceEndPos      if   notSpaceStartPos  gt  notSpaceEndPos     s       return        s   s substr notSpaceStartPos  notSpaceEndPos - notSpaceStartPos   1          reduce multiple spaces between two words to a single space      string temp      for   int i   0  i  lt  s length    i               if   i  gt  0  amp  amp  s i          amp  amp  s i-1           continue          temp push back s i              s   temp      I have used this method to pass a LeetCode problem Reverse Words in a String

User · Answer

Here is how you can do it   std  string  amp  trim std  string  amp  str       return ltrim rtrim str        And the supportive functions are implemeted as   std  string  amp  ltrim std  string  amp  str      auto it2    std  find if  str begin     str end        char ch   return  std  isspace lt char gt  ch   std  locale  classic              str erase  str begin     it2     return str        std  string  amp  rtrim std  string  amp  str      auto it1    std  find if  str rbegin     str rend        char ch   return  std  isspace lt char gt  ch   std  locale  classic              str erase  it1 base     str end        return str         And once you ve all these in place  you can write this  as well   std  string trim copy std  string const  amp  str       auto s   str     return ltrim rtrim s        Try this

User · Answer

This is my solution for stripping the leading and trailing spaces      std  string stripString      Plamen        while  stripString empty    amp  amp  std  isspace  stripString begin         stripString erase stripString begin      while  stripString empty    amp  amp  std  isspace  stripString rbegin         stripString erase stripString length  -1     The result is  Plamen

User · Answer

To add to the problem  how to extend this formatting to process extra spaces between words of the string   Actually  this is a simpler case than accounting for multiple leading and trailing white-space characters  All you need to do is remove duplicate adjacent white-space characters from the entire string  The predicate for adjacent white space would simply be  auto by space      unsigned char a  unsigned char b        return std  isspace a  and std  isspace b       and then you can get rid of those duplicate adjacent white-space characters with std  unique  and the erase-remove idiom     s    quot        This       is       a sample   string      quot    s erase std  unique std  begin s   std  end s   by space            std  end s       s    quot  This is a sample string  quot     This does potentially leave an extra white-space character at the front and or the back  This can be removed quite easily  if  std  size s   amp  amp  std  isspace s back         s pop back     if  std  size s   amp  amp  std  isspace s front         s erase 0  1    Here s a demo

User · Answer

What about the erase-remove idiom   std  string s         s erase  std  remove s begin    s end          s end        Sorry  I saw too late that you don t want to remove all whitespace

User · Answer

Using the standard library has many benefits  but one must be aware of some special cases that cause exceptions  For example  none of the answers covered the case where a C   string has some Unicode characters  In this case  if you use the function isspace  an exception will be thrown   I have been using the following code for trimming the strings and some other operations that might come in handy  The major benefits of this code are  it is really fast  faster than any code I have ever tested   it only uses the standard library  and it never causes an exception    include  lt string gt   include  lt algorithm gt   include  lt functional gt   include  lt locale gt   include  lt iostream gt   typedef unsigned char BYTE   std  string strTrim std  string s  char option   0           convert all whitespace characters to a standard space     std  replace if s begin    s end     std  function lt int BYTE  gt    isspace                remove leading and trailing spaces     size t f   s find first not of           if  f    std  string  npos  return         s   s substr f  s find last not of      - f   1           remove consecutive spaces     s   std  string s begin    std  unique s begin    s end               BYTE l  BYTE r   return l         amp  amp  r                   switch  option            case  l       convert to lowercase         std  transform s begin    s end    s begin      tolower           return s      case  U       convert to uppercase         std  transform s begin    s end    s begin      toupper           return s      case  n       remove all spaces         s erase std  remove s begin    s end          s end             return s      default     just trim         return s

User · Answer

For leading- and trailing spaces  how about   string string trim const string amp  in         stringstream ss      string out      ss  lt  lt  in      ss  gt  gt  out      return out       Or for a sentence   string trim words const string amp  sentence        stringstream ss      ss  lt  lt  sentence      string s      string out       while ss  gt  gt  s             out   s                 return out substr 0  out length  -1

User · Answer

char  str    char   malloc 50   sizeof char        strcpy str       some random string   lt 50 chars            while  str            str      t      str      n               str         int len   strlen str        while len  gt   0  amp  amp                str len - 1            str len - 1       t      str      n                       str   len - 1      0               len--             printf    s  n   str

User · Answer

I am currently using these functions      trim from left inline std  string amp  ltrim std  string amp  s  const char  t      t n r f v         s erase 0  s find first not of t        return s        trim from right inline std  string amp  rtrim std  string amp  s  const char  t      t n r f v         s erase s find last not of t    1       return s        trim from left  amp  right inline std  string amp  trim std  string amp  s  const char  t      t n r f v         return ltrim rtrim s  t   t         copying versions  inline std  string ltrim copy std  string s  const char  t      t n r f v         return ltrim s  t      inline std  string rtrim copy std  string s  const char  t      t n r f v         return rtrim s  t      inline std  string trim copy std  string s  const char  t      t n r f v         return trim s  t

User · Answer

This might be the simplest of all   You can use string  find and string  rfind to find whitespace from both sides and reduce the string   void TrimWord std  string amp  word        if  word empty    return          Trim spaces from left side     while  word find         0                word erase 0  1                 Trim spaces from right side     size t len   word size        while  word rfind         --len                word erase len  len   1

User · Answer

neat and clean    void trimLeftTrailingSpaces string  amp input            input erase input begin    find if input begin    input end       int ch                return  isspace ch                           void trimRightTrailingSpaces string  amp input            input erase find if input rbegin    input rend       int ch                return  isspace ch              base    input end

[c++] Removing leading and trailing spaces from a string

Examples related to c++

Examples related to string