C++ string to int Conversion
We can convert string to int in multiple ways. The easiest way to do this is by using the std::stoi() function introduced in C++11.
Example 1: C++ string to int Using stoi()
#include <iostream>
#include <string>
int main() {
std::string str = "123";
int num;
// using stoi() to store the value of str1 to x
num = std::stoi(str);
std::cout << num;
return 0;
}
Output
123
Example 2: char Array to int Using atoi()
We can convert a char array to int using the std::atoi() function. The atoi() function is defined in the cstdlib header file.
#include <iostream>
// cstdlib is needed for atoi()
#include <cstdlib>
using namespace std;
int main() {
// declaring and initializing character array
char str[] = "456";
int num = std::atoi(str);
std::cout << "num = " << num;
return 0;
}
Output
num = 456
To learn other ways of converting strings to integers, visit Different Ways to Convert C++ string to int
C++ int to string Conversion
We can convert int to string using the C++11 std::to_string() function. For older versions of C++, we can use std::stringstream objects.
Example 3: C++ int to string Using to_string()
#include <iostream>
#include <string>
using namespace std;
int main() {
int num = 123;
std::string str = to_string(num);
std::cout << str;
return 0;
}
Output
123
Example 4: C++ int to string Using stringstream
#include <iostream>
#include<string>
#include<sstream> // for using stringstream
using namespace std;
int main() {
int num = 15;
// creating stringstream object ss
std::stringstream ss;
// assigning the value of num to ss
ss << num;
// initializing string variable with the value of ss
// and converting it to string format with str() function
std::string strNum = ss.str();
std::cout << strNum;
return 0;
}
Output
15
To know about converting a string to float/double, visit C++ String to float/double.