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C++ <cmath>

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C++ String (string) and int (integer) interconversion

In this tutorial, we will learn how to convert String (string) and int (integer) by using examples.

C ++string (string) to int (integer)

We can convert string and int in many ways. The simplest method is to useC ++ 11instd::stoi() introduced features.

Example1: Use stoi() to convert C ++Convert string to int

Example

#include <iostream>
#include <string>
int main() {
　　　　std::string str = "123";
　　　　int num;
　　　　//　Use stoi() to convert str1The value is stored in x
　　　　num = std::stoi(str);
　　　　std::cout << num;
　　　　return 0;
}

Output Result

Example2: Use atoi() to convert a char array to int

We can use the std::atoi() function to convert a char array to int. The atoi() function is defined in the std::cstdlib header file.

Example

#include <iostream>
//　atoi() requires std::cstdlib
#include <cstdlib>
using namespace std;
int main() {
　　　　//　Declare and initialize a character array
　　　　char str[] = "456";
　　　　int num = std::atoi(str);
　　　std::cout << "num = " << num;
　　　　
　　　　return 0;
}

Output Result

num =　456

C ++ int (integer) to string (string)

We can use C ++ 11 std::to_string() function converts int to string. For older versions of C ++, we can use the std::stringstream object.

Example3: Use to_string() to convert C ++ Convert int to string

Example

#include <iostream>
#include <string>
using namespace std;
int main() {
　　　　int num =　123;
　　　　
　　　　std::string str = to_string(num);
　　　　std::cout << str;
　　　　return 0;
}

Output Result

Example4: Use stringstream to convert C ++ Convert int to string

Example

#include <iostream>
#include <string>
#include <sstream>　//　To use stringstream
using namespace std;
int main() {
　　　　int num =　15;
　　
　　　　//　Create a stringstream object ss
　　　　std::stringstream ss;
　　
　　　　//　Assign the value of num to ss
　　　　ss << num;
　　
　　　　　//Initialize the string variable with the value of ss
　　　　　//Then use the str() function to convert it to string format
　　　　std::string str = ss.str();
　　　　std::cout << str;
　　　　return 0;
}

Output Result

To learn about converting strings to float / For information on double, please visitC ++ String Conversion to float / double.

C++ Vector (Vector)c++ Keywords and Identifiers