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Stoi function in C++

The C++ std::stoi function is part of the C++ Standard Library and is used to convert a string to an integer (int). It stands for “string to integer.” The std::stoi function takes a string as input, parses it, and returns the corresponding integer value. Here’s how to use it:

#include <iostream>
#include <string>

int main() {
    std::string str = "12345"; // Input string containing an integer

    try {
        int intValue = std::stoi(str); // Convert the string to an integer
        std::cout << "Integer value: " << intValue << std::endl;
    } catch (const std::invalid_argument& e) {
        std::cerr << "Invalid argument: " << e.what() << std::endl;
    } catch (const std::out_of_range& e) {
        std::cerr << "Out of range: " << e.what() << std::endl;

    return 0;

In this example:

  • We include the necessary headers, <iostream> and <string>.
  • We have a string str containing the text representation of an integer.
  • We use a try-catch block to handle potential exceptions that may occur during the conversion.
  • Inside the try block, we call std::stoi(str) to convert the string to an integer.
  • If the conversion is successful, we print the integer value.
  • If an invalid argument or an out-of-range value is encountered during the conversion, it will throw an exception, and we handle it in the catch blocks.

The std::stoi function is a safe and convenient way to convert a string to an integer while also handling potential errors gracefully. It’s a commonly used function when dealing with string parsing and integer conversion in C++.


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