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break a string up c++

Posted on 2006-11-02
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746 Views
Last Modified: 2008-02-01
C++
Okay heres my code:

string line = "120 520 36 4 55 -1"
string strNum;

I want strNum to pull each number at a time by whitespace.
so first time would be 120 next 520 and so on.
How would you suggest going about this?
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Question by:xneo27
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7 Comments
 
LVL 86

Expert Comment

by:jkr
ID: 17860288
The easiest way: Use a 'stringstream', e.g.

#include <sstream>

string line = "120 520 36 4 55 -1"
string strNum;

stringstream ss;
int i = 0;

ss << line;

while(!ss.eof()) {

ss >> strNum;

cout << i << " -> " << strNum << endl;

++i;
}

You could even use an 'int num;', e.g.

#include <sstream>

string line = "120 520 36 4 55 -1"
int num;

stringstream ss;
int i = 0;

ss << line;

while(!ss.eof()) {

ss >> num;

cout << i << " -> " << num << endl;

++i;
}
0
 

Author Comment

by:xneo27
ID: 17861187
Is there a way to do this without the use of sstream, I cant use it in my current project?
0
 
LVL 86

Expert Comment

by:jkr
ID: 17861286
Sure, there are plenty of ways to do that, with 'strtok()' proabaly being the most common one:

#include <string.h>

string line = "120 520 36 4 55 -1"
string strNum;

char seps[]   = " ";
char *token;
char* tmp = strdup(line.c_str());

   /* Establish string and get the first token: */
   token = strtok( tmp, seps );
   while( token != NULL )
   {
      /* While there are tokens in "tmp" */
      strNum = = token;
      cout << strNum << endl;
      /* Get next token: */
      token = strtok( NULL, seps );
   }

free(tmp);
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LVL 86

Accepted Solution

by:
jkr earned 500 total points
ID: 17861685
BTW, another option would be a function like

#include <string>
#include <vector>
#include <iostream>

using namespace std;

int split_text(string strIn, const char cDelim, vector<string>& vResult) {

   int nPos = 0;
   int nCount = 0;
   int nFound;
   string strToken;

   while(1) {

      nFound = strIn.find(cDelim,nPos);

      if (-1 == nFound)  {

        strToken = strIn.substr(nPos,strIn.length() - nPos);
        vResult.push_back(strToken);
        break;
      }

      strToken = strIn.substr(nPos,nFound - nPos);

      nPos = nFound + 1;

      ++nCount;

      vResult.push_back(strToken);

   }

   return nCount;
}

int main () {

  string line = "120 520 36 4 55 -1";
  vector<string> vResult;

   int n = split_text(line,' ',vResult);

   for ( int i = 0; i < n; ++i)
      cout << vResult[i] << endl;
}
0
 
LVL 6

Expert Comment

by:_iskywalker_
ID: 17865226
if you know how many numbers you are expecting you may use, sscanf:
            
char* line = "120 520 36 4 55 -1"
int N[6],i;
sscanf(line,"%i %i %i %i %i %i",N[0],N[1],N[2],N[3],N[4],N[5]);
for (i=0;i<6;i++){
count << N[i];
}
cout << endl;
0
 
LVL 12

Expert Comment

by:rajeev_devin
ID: 17865397
Another way is to do like this

void split(const std::string& str,
               std::vector<std::string>& tokens,
               const std::string& delimiters = " ")
{
    std::string::size_type lastPos = str.find_first_not_of(delimiters, 0);
    std::string::size_type pos = str.find_first_of(delimiters, lastPos);
      
    while (std::string::npos != pos || std::string::npos != lastPos)
    {
        tokens.push_back(str.substr(lastPos, pos - lastPos));
        lastPos = str.find_first_not_of(delimiters, pos);
        pos = str.find_first_of(delimiters, lastPos);
    }
}

...
std::string line = "120 520 36 4 55 -1";
std::vector<std::string> result;
split(line, result);
0
 

Author Comment

by:xneo27
ID: 17899141
Thanks that helped alot.
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