c++ typecast string to int code example

Example 1: string to int c++

#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;
}

Example 2: string to number in c++

// For C++11 and later versions
string str1 = "45"; 
string str2 = "3.14159"; 
string str3 = "31337 geek"; 

int myint1 = stoi(str1); 
int myint2 = stoi(str2); 
int myint3 = stoi(str3); 

// Output
stoi("45") is 45
stoi("3.14159") is 3
stoi("31337 geek") is 31337

Example 3: c++ string to int

atoi( str.c_str() )

Example 4: how to convert from string to int in c++

#include <iostream>
#include <sstream>

using namespace std;

int main() {
    string s = "999";

    stringstream degree(s);

    int x = 0;
    degree >> x;

    cout << "Value of x: " << x;
}

Example 5: string to int c++

// stoi example
#include <iostream>   // std::cout
#include <string>     // std::string, std::stoi

int main ()
{
  std::string str_dec = "2001, A Space Odyssey";
  std::string str_hex = "40c3";
  std::string str_bin = "-10010110001";
  std::string str_auto = "0x7f";

  std::string::size_type sz;   // alias of size_t

  int i_dec = std::stoi (str_dec,&sz);
  int i_hex = std::stoi (str_hex,nullptr,16);
  int i_bin = std::stoi (str_bin,nullptr,2);
  int i_auto = std::stoi (str_auto,nullptr,0);

  std::cout << str_dec << ": " << i_dec << " and [" << str_dec.substr(sz) << "]\n";
  std::cout << str_hex << ": " << i_hex << '\n';
  std::cout << str_bin << ": " << i_bin << '\n';
  std::cout << str_auto << ": " << i_auto << '\n';

  return 0;
}