I need to create a function that gets those numbers in the string

Question

I'm trying to make a function that takes an argument should be something like this

string s1 = "[1 -2.5 3;4 5.25 6;7 8 9.12]";

It's supposed to return it to be only the numbers only without the semicolons or the [ and ] and spaces

Like this:

1 -2.5 3 4 5.25 6 7 8 9.12 

So I can later convert the string to float and save them into an array

Any ideas?

#include <iostream>
#include <string>
using namespace std;


string s1 = "[1 -2.5 3;4 5.25 6;7 8 9.12]";

void cutter(string s){


    for(int i=1;i<s.length();i++){
        if(i != s.find(" ") &&  i != s.find(";") ){
            cout << s[i];
            s.erase(0,i-1);

        }
        else if(i == s.find(" ") || i == s.find(";") ){
            cout<<endl;

        }


    }

}

int main()
{
    cutter(s1);
    return 0;
}

Answer 1

To remove the [ and ] and also replace the ; with spaces you can do something like this:

#include <algorithm>

void cutter(string &s) {
    s.erase(std::remove(s.begin(), s.end(), '['), s.end());
    s.erase(std::remove(s.begin(), s.end(), ']'), s.end());
    std::replace(s.begin(), s.end(), ';', ' ');
}

No need for any manual loops over the string. Also note that in the signature of the function, you need string &s, not string s. Without that & you're passing a copy of the string to the function and that copy is discarded at the end, resulting in no change to the original. With the & you pass a reference instead and the program works as intended.

---

Of course, you could also keep it pass by copy and instead return the modified string:

std::string cutter(std::string s) {
    // modify the string here
    return s; // returns the modified copy
}

And in main, do:

s1 = cutter(s1); // assign the result to the original to change it

Answer 2

If you have boost, then this is almost trivial:

std::vector<std::string> result;

boost::remove_erase_if(s1, boost::is_any_of("[]"));

boost::split(result, s1, boost::is_any_of(" ;"));

you might want to take a copy of s1 though as it will be mutated in this example.

Answer 3

Below is a solution that uses two functions.

One function returns a new string without [, ] and ;

The other function converts a string with float values to a vector of floats.

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

std::string s1 = "[1 -2.5 3;4 5.25 6;7 8 9.12]";

std::string cutter(std::string &s){
    std::string res = "";
    for (auto c : s)                                 // Loop over all chars in s
    {
        if (c == ';') res += ' ';                    // Replace ; with space
        else if ((c != '[') && (c != ']')) res += c; // Skip [ and ]
    }
    return res;
}

std::vector<float> string_to_floats(std::string &s)
{
      float f;
      std::vector<float> res;

      std::stringstream stream(s);        // Create and initialize the stream
      while(1)
      {
          stream >> f;                    // Try to read a float
          if (stream.fail()) return res;  // If it failed, return the result
          res.push_back(f);               // Save the float in the result vector
      }
}

int main()
{
    std::string s2 = cutter(s1);
    std::cout << s2 << std::endl;

    std::vector<float> values = string_to_floats(s2);
    std::cout << "Number of floats: " << values.size() << std::endl;
    for (auto f : values) std::cout << f << std::endl;

    return 0;
}

Output:

1 -2.5 3 4 5.25 6 7 8 9.12
Number of floats: 9
1
-2.5
3
4
5.25
6
7
8
9.12

Answer 4

and here's a regex based solution (c++11 and above):

#include <iostream>
#include <regex>

using namespace std;

string cutter(string src) {
 string out, dlm;
 regex e(R"(-?\d+\.?\d*)");
 smatch m;

 while(regex_search(src,m,e)) {
  for(const auto &x: m) 
   { out += dlm + string(x); dlm = ' '; }
  src = m.suffix().str();
 }

 return out;
}

int main()
{
 string s1 = "[1 -2.5 3;4 5.25 6;7 8 9.12]";

 cout << cutter(move(s1)) << endl;   
 return 0;
}

output:

1 -2.5 3 4 5.25 6 7 8 9.12

Plus, solution based on removal of extra chars (but the first one idiomatically is more preferable):

#include <iostream>
#include <regex>

using namespace std;

string cutter(const string &src) {
 regex e("[ ;]+");
 string out = std::regex_replace(src,e," ");
 return out.substr(1, out.size()-2);
}

int main()
{
 string s1 = "[1 -2.5 3;4 5.25 6;7 8 9.12]";

 cout << cutter(s1) << endl;   
 return 0;
}