How to remove all substrings from a string

This is a basic question and you'd better take a look at the string capabilities in the standard library.

Classic solution

#include <iostream>
#include <string>

int main() { 
   std::string str = "red tuna, blue tuna, black tuna, one tuna";
   std::string pattern = "tuna";

   std::string::size_type i = str.find(pattern);
   while (i != std::string::npos) {
     str.erase(i, pattern.length());
     i = str.find(pattern, i);
   }

   std::cout << str;
}

Example

RegEx solution

Since C++11 you have another solution (thanks Joachim for reminding me of this) based on regular expressions

#include <iostream>
#include <string>
#include <regex>

int main() { 
   std::string str = "red tuna, blue tuna, black tuna, one tuna";
   std::regex pattern("tuna");

   std::cout << std::regex_replace(str, pattern, "");
}

Example

Removes all instances of the pattern from a string,

#include <string>
#include <iostream>

using namespace std;

void removeSubstrs(string& s, string& p) { 
  string::size_type n = p.length();
  for (string::size_type i = s.find(p);
      i != string::npos;
      i = s.find(p))
      s.erase(i, n);
}

int main() {

  string str = "red tuna, blue tuna, black tuna, one tuna";
  string pattern = "tuna";

  removeSubstrs(str, pattern);
  cout << str << endl;
}