Parsing a comma-delimited std string

Question

If I have a std  string containing a comma-separated list of numbers  what s the simplest way to parse out the numbers and put them in an integer array   I don t want to generalise this out into parsing anything else  Just a simple string of comma separated integer numbers such as  1 1 1 1 2 1 1 1 0

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simple structure  easily adaptable  easy maintenance     std  string stringIn    my csv  is 10233478 separated by commas   std  vector lt std  string gt  commaSeparated 1   int commaCounter   0  for  int i 0  i lt stringIn size    i          if  stringIn i                    commaSeparated push back              commaCounter          else           commaSeparated at commaCounter     stringIn i             in the end you will have a vector of strings with every element in the sentence separated by spaces   empty strings are saved as separate items

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Input one number at a time  and check whether the following character is     If so  discard it    include  lt vector gt   include  lt string gt   include  lt sstream gt   include  lt iostream gt   int main         std  string str    1 2 3 4 5 6       std  vector lt int gt  vect       std  stringstream ss str        for  int i  ss  gt  gt  i             vect push back i               if  ss peek                       ss ignore               for  std  size t i   0  i  lt  vect size    i            std  cout  lt  lt  vect i   lt  lt  std  endl

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string exp    token1 token2 token3   char delimiter        vector lt string gt  str  string acc       for int i   0  i  lt  exp size    i          if exp i     delimiter                str push back acc           acc                 else         acc    exp i

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I m surprised no one has proposed a solution using std  regex yet    include  lt string gt   include  lt algorithm gt   include  lt vector gt   include  lt regex gt   void parse csint  const std  string amp  str  std  vector lt int gt  amp  result          typedef std  regex iterator lt std  string  const iterator gt  re iterator      typedef re iterator  value type re iterated       std  regex re     d           re iterator rit  str begin    str end    re        re iterator rend       std  transform  rit  rend  std  back inserter result                const re iterated amp  it    return std  stoi it 1              This function inserts all integers at the back of the input vector  You can tweak the regular expression to include negative integers  or floating point numbers  etc

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I cannot yet comment  getting started on the site  but added a more generic version of Jerry Coffin s fantastic ctype s derived class to his post   Thanks Jerry for the super idea    Because it must be peer-reviewed  adding it here too temporarily   struct SeparatorReader  std  ctype lt char gt        template lt typename T gt      SeparatorReader const T  amp seps   std  ctype lt char gt  get table seps   true          template lt typename T gt      std  ctype base  mask const  get table const T  amp seps            auto  amp  amp rc   new std  ctype base  mask std  ctype lt char gt   table size             for auto  amp  amp sep  seps              rc static cast lt unsigned char gt  sep     std  ctype base  space          return  amp rc 0

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This is the simplest way  which I used a lot  It works for any one-character delimiter    include lt bits stdc   h gt  using namespace std   int main        string str      cin  gt  gt  str     int temp     vector lt int gt  result     char ch     stringstream ss str       do             ss gt  gt temp         result push back temp       while ss gt  gt ch       for int i 0   i  lt  result size     i           cout lt  lt result i  lt  lt endl      return 0

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Something less verbose  std and takes anything separated by a comma   stringstream ss   1 1 1 1  or something else  1 1 1 0     vector lt string gt  result   while  ss good           string substr      getline  ss  substr             result push back  substr

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You could also use the following function   void tokenize const string amp  str  vector lt string gt  amp  tokens  const string amp  delimiters               Skip delimiters at beginning    string  size type lastPos   str find first not of delimiters  0         Find first non-delimiter    string  size type pos   str find first of delimiters  lastPos      while  string  npos    pos    string  npos    lastPos           Found a token  add it to the vector      tokens push back str substr lastPos  pos - lastPos            Skip delimiters      lastPos   str find first not of delimiters  pos           Find next non-delimiter      pos   str find first of delimiters  lastPos

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void ExplodeString  const std  string amp  string  const char separator  std  list lt int gt  amp  result         if  string size               std  string  const iterator last   string begin            for  std  string  const iterator i string begin    i  string end      i                 if   i    separator                     const std  string str last i                   int id   atoi str c str                     result push back id                   last   i                     last                                  if  last    string end     result push back  atoi  amp  last

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bool GetList  const std  string amp  src  std  vector lt int gt  amp  res          using boost  lexical cast      using boost  bad lexical cast      bool success   true      typedef boost  tokenizer lt boost  char separator lt char gt   gt  tokenizer      boost  char separator lt char gt  sepa           tokenizer tokens src  sepa       for  tokenizer  iterator tok iter   tokens begin              tok iter    tokens end      tok iter          try           res push back lexical cast lt int gt   tok iter                  catch  bad lexical cast  amp             success   false                    return success

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Lots of pretty terrible answers here so I ll add mine  including test program     include  lt string gt   include  lt iostream gt   include  lt cstddef gt   template lt typename StringFunction gt  void splitString const std  string  amp str  char delimiter  StringFunction f      std  size t from   0    for  std  size t i   0  i  lt  str size      i        if  str i     delimiter          f str  from  i         from   i   1              if  from  lt   str size        f str  from  str size         int main int argc  char  argv          if  argc    2          return 1       splitString argv 1           const std  string  amp s  std  size t from  std  size t to            std  cout  lt  lt       lt  lt  s substr from  to - from   lt  lt     n                return 0      Nice properties    No dependencies  e g  boost  Not an insane one-liner Easy to understand  I hope  Handles spaces perfectly fine Doesn t allocate splits if you don t want to  e g  you can process them with a lambda as shown  Doesn t add characters one at a time - should be fast  If using C  17 you could change it to use a std  stringview and then it won t do any allocations and should be extremely fast    Some design choices you may wish to change    Empty entries are not ignored  An empty string will call f   once    Example inputs and outputs           - gt                 - gt              1      - gt      1        1      - gt      1           - gt           1  2   - gt      1     2               - gt

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Simple Copy Paste function  based on the boost tokenizer   void strToIntArray std  string string  int  array  int array len      boost  tokenizer lt  gt  tok string     int i   0    for boost  tokenizer lt  gt   iterator beg tok begin    beg  tok end     beg       if i  lt  array len        array i    atoi beg- gt c str         i

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Alternative solution using generic algorithms and Boost Tokenizer   struct ToInt       int operator   string const  amp str    return atoi str c str           string values    1 2 3 4 5 9 8 7 6    vector lt int gt  ints  tokenizer lt  gt  tok values    transform tok begin    tok end    back inserter ints   ToInt

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std  string input  1 1 1 1 2 1 1 1 0   std  vector lt long gt  output  for std  string  size type p0 0 p1 input find               p1  std  string  npos    p0  std  string  npos           p0  p1  std  string  npos  p1   p1  p1 input find     p0        output push back  strtol input c str   p0 NULL 0       It would be a good idea to check for conversion errors in strtol    of course  Maybe the code may benefit from some other error checks as well

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include  lt sstream gt   include  lt vector gt   include  lt algorithm gt   include  lt iterator gt   const char  input      29870 1 abc 2 1 1 1 0   int main         std  stringstream ss input       std  vector lt int gt  output      int i      while    ss eof                  int c    ss peek            if   c  lt   0     c  gt   9                       ss ignore 1             continue                    if  ss  gt  gt  i                     output push back i                         std  copy output begin    output end    std  ostream iterator lt int gt   std  cout              return 0

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Yet another  rather different  approach  use a special locale that treats commas as white space    include  lt locale gt   include  lt vector gt   struct csv reader  std  ctype lt char gt        csv reader    std  ctype lt char gt  get table           static std  ctype base  mask const  get table             static std  vector lt std  ctype base  mask gt  rc table size  std  ctype base  mask              rc        std  ctype base  space          rc   n     std  ctype base  space          rc        std  ctype base  space          return  amp rc 0               To use this  you imbue   a stream with a locale that includes this facet  Once you ve done that  you can read numbers as if the commas weren t there at all  Just for example  we ll read comma-delimited numbers from input  and write then out one-per line on standard output    include  lt algorithm gt   include  lt iterator gt   include  lt iostream gt   int main         std  cin imbue std  locale std  locale    new csv reader          std  copy std  istream iterator lt int gt  std  cin                  std  istream iterator lt int gt                   std  ostream iterator lt int gt  std  cout    n         return 0

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include  lt sstream gt   include  lt vector gt   const char  input    1 1 1 1 2 1 1 1 0    int main         std  stringstream ss input       std  vector lt int gt  output      int i      while  ss  gt  gt  i            output push back i           ss ignore 1             Bad input  for instance consecutive separators  will mess this up  but you did say simple

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The C   String Toolkit Library  Strtk  has the following solution to your problem    include  lt string gt   include  lt deque gt   include  lt vector gt   include  strtk hpp  int main         std  string int string    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15      std  vector lt int gt  int list     strtk  parse int string     int list       std  string double string    123 456 789 012 345 678 901 234 567 890      std  deque lt double gt  double list     strtk  parse double string     double list       return 0      More examples can be found Here

[c++] Parsing a comma-delimited std::string

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