How Can I Efficiently Extract Integers from a Comma-Separated String in C ?

Extracting Numeric Data from Comma-Delimited Strings in C

Parsing data from comma-separated strings into numerical arrays presents a common challenge in programming. For the specific case of integer numbers, C provides several straightforward approaches.

Basic Parsing Algorithm:

One simple method involves iterating through the string character by character. For each character, check if the next character is a comma. If it is, discard the comma. Otherwise, convert the character to an integer and store it in the array.

Using istringstream:

The C Standard Library offers the istringstream class for parsing input streams. To extract numbers from a comma-delimited string, create an istringstream object with the string as input. Then, use the stream extraction operator >> to extract each number one at a time.

Implementation:

The following code snippet demonstrates the basic parsing algorithm using istringstream:

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

int main()
{
    std::string str = "1,2,3,4,5,6";
    std::vector<int> vect;

    std::stringstream ss(str);

    for (int i; ss >> i;) {
        vect.push_back(i);    
        if (ss.peek() == ',')
            ss.ignore();
    }

    for (std::size_t i = 0; i < vect.size(); i++)
        std::cout << vect[i] << std::endl;

    return 0;
}

Other Options:

For more complex parsing scenarios, the C Standard Library provides additional options, such as the strtok function and regular expressions. However, for simple comma-delimited integer lists, the above methods are typically sufficient and straightforward to implement.

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