how to string to integer in c 2b 2b

1#include <iostream>
2#include <string>
3
4int main() {
5
6    std::string str = "123";
7    int num;
8
9    // using stoi() to store the value of str1 to x
10    num = std::stoi(str);
11
12    std::cout << num;
13
14    return 0;
15}

1// For C++11 and later versions
2string str1 = "45"; 
3string str2 = "3.14159"; 
4string str3 = "31337 geek"; 
5
6int myint1 = stoi(str1); 
7int myint2 = stoi(str2); 
8int myint3 = stoi(str3); 
9
10// Output
11stoi("45") is 45
12stoi("3.14159") is 3
13stoi("31337 geek") is 31337 

1#include<string>
2string str1 = "45"; 
3string str2 = "3.14159"; 
4string str3 = "31337 geek";
5
6int myint1 = stoi(str1);
7std::cout<<stoi(str1);

1// EXAMPLE
2std::string sStringAsString = "789";
3int iStringAsInt = atoi( sStringAsString.c_str() );
4
5/* SYNTAX
6atoi( <your-string>.c_str() )
7*/
8
9/* HEADERS
10#include <cstring>
11#include <string>
12*/