How to Parse a Comma Separated String Sequence in C++

1. Use std::string::find and std::string::erase Functions to Parse Comma Separated String Sequence in C++
2. Use std::getline Function to Parse Comma Separated String Sequence

This article will demonstrate multiple methods about how to parse a comma-separated string sequence in C++.

Use std::string::find and std::string::erase Functions to Parse Comma Separated String Sequence in C++

The std::find method is a built-in function of the std::string class, and it can be utilized to find the position of the given substring. It takes a single argument in this case which denotes the substring to be found. Any multi-character string variable can be initialized to be passed as an argument. Although, in the following example, we declare a single comma containing string. Since the find method returns the position of the substring and string::npos when the substring is not found, we can put the comparison expression in a while loop that’s gonna execute until the expression evaluates true.

We also store the parsed string on each iteration in the vector container. Then, the erase method is called to delete the characters before and including the first found comma delimiter in order to continue processing the same string object in the next iteration. Finally, we output the stored elements in the vector to the cout stream.

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

using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::stringstream;
using std::vector;

int main() {
  string text = "1,2,3,4,5,6,7,8,9,10";
  string delimiter = ",";
  vector<string> words{};

  size_t pos = 0;
  while ((pos = text.find(delimiter)) != string::npos) {
    words.push_back(text.substr(0, pos));
    text.erase(0, pos + delimiter.length());
  }
  for (const auto &str : words) {
    cout << str << endl;
  }

  return EXIT_SUCCESS;
}

Output:

1
2
3
4
5
6
7
8
9

Use std::getline Function to Parse Comma Separated String Sequence

The previous solution misses extracting the last number inf the comma-separated sequence. So it might be better to use the following method using the std::getline function rather than add a conditional check in the previous code example. getline reads characters from the given input stream and stores them into a string object. The function also takes an optional third argument to specify the delimiter by which to split input string. We also store the extracted strings in the std::vector container on each iteration for later usage.

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

using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::stringstream;
using std::vector;

int main() {
  string text = "1,2,3,4,5,6,7,8,9,10";
  char delimiter = ',';
  vector<string> words{};

  stringstream sstream(text);
  string word;
  while (std::getline(sstream, word, delimiter)) {
    words.push_back(word);
  }

  for (const auto &str : words) {
    cout << str << endl;
  }

  return EXIT_SUCCESS;
}

Output:

1
2
3
4
5
6
7
8
9
10