CPP

convert stirng to int c++

int thing = std::stoi(string);

string to int c++

int number = std::stoi(string, base);  // str to int
int number = std::stoi("100",10);  // number = 100

long int number = std::strtol(string, endptr, base);  // str to long int

convert string to number c++

#include <iostream>
#include <sstream>
using namespace std;
int main()
{
	string str = "123456";
 	int n;
  	stringstream ( str ) >> n;
	cout << n; //Output:123456
	return 0;
}

string to int c++

int number = std::stoi(string);  // str to int
int number = std::stoi("100");  // number = 100

string to integer convert c++

#include <iostream>
#include <string>
using namespace std;

int main() {
   // a string variable named str
   string str = "7";
   //print to the console
   cout << "I am a string " << str << endl;

   //convert the string str variable to have an int value
   //place the new value in a new variable that holds int values, named num
   int num = stoi(str);
   
   //print to the console
   cout << "I am an int " << num << endl;
}

convert string to number c++

//stoi() : The stoi() function takes a string as an argument and 
//returns its value. Supports C++11 or above. 
// If number > 10^9 , use stoll().
#include <iostream>
#include <string>
using namespace std;
main() {
	string str = "12345678";
	cout << stoi(str);
}

how to string to integer in c++

#include<string>
string str1 = "45"; 
string str2 = "3.14159"; 
string str3 = "31337 geek";

int myint1 = stoi(str1);
std::cout<<stoi(str1);

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 

string to int in c++

#include <iostream>
#include <string>
using namespace std;
int main() {
 
    string s = "10";
 
    try
    {
        int i = stoi(s);
        cout << i << '
';
    }
    catch (invalid_argument const &e)
    {
        cout << "Bad input: std::invalid_argument thrown" << '
';
    }
    catch (out_of_range const &e)
    {
        cout << "Integer overflow: std::out_of_range thrown" << '
';
    }
 
    return 0;
}

C++ String to int Conversion

#include <iostream>
#include <string>

int main() {

    std::string str = "12345";
    int num;
    
    num = std::stoi(str);

    std::cout << num;

    return 0;
}

string to int c++

// Convert 2 character substring from position 0 to an integer
int num = std::stoi(s.substr(0, 2));

string to int c++

// Both functions work identically though you'll need to use "#include <string>" 
atoi( str.c_str() );
stoi( str );

c++ string to int

// EXAMPLE
std::string sStringAsString = "789";
int iStringAsInt = atoi( sStringAsString.c_str() );

/* SYNTAX
atoi( <your-string>.c_str() )
*/

/* HEADERS
#include <cstring>
#include <string>
*/

how to code string to int converter c++

string str;
int ans = 0;
int currPower = 0;
for(int i = str.size()-1; i >= 0; i--){
	ans += (str[i] - '0') * pow(10,currPower);
    currPower++;
}

string to int c++

#include <sstream>
using namespace std;
int main()
{
    stringstream string_to_int;
    string s1="12345";
    int n1;

    string_to_int<<s1;
    //也可以使用string_to_int.str(s1);
    //或者 s1=string_to_int.str();
    
    string_to_int>>n1;

    cout<<"s1="<<s1<<endl;//s1=12345
    cout<<"n1="<<n1<<endl;//n1=12345
    
}

string to integer in c++

// C++ program to demonstrate working of stoi()
// Work only if compiler supports C++11 or above
// Because STOI() was added in C++ after 2011
#include <iostream>
#include <string>
using namespace std;
  
int main()
{
    string str1 = "45";
    string str2 = "3.14159";
    string str3 = "31337 geek";
  
    int myint1 = stoi(str1); // type of explicit type casting
    int myint2 = stoi(str2); // type of explicit type casting
    int myint3 = stoi(str3); // type of explicit type casting
  
    cout << "stoi("" << str1 << "") is " << myint1
         << '
';
    cout << "stoi("" << str2 << "") is " << myint2
         << '
';
    cout << "stoi("" << str3 << "") is " << myint3
         << '
';
  
    return 0;
}

c++ string to int

atoi( str.c_str() )

string to int c++

string str1 = "45";
    string str2 = "3.14159";
    string str3 = "31337 geek";
 
    int myint1 = stoi(str1); // type of explicit type casting
    int myint2 = stoi(str2); // type of explicit type casting
    int myint3 = stoi(str3); // type of explicit type casting
/* Result
45
3
31337
*/

string to int c++

std::stoi( str )

how to convert string to int in c++

string s = "123";
int n = s.size();
int num = 0;
 for(int i = 0 ; i<n;i++)//this what stoi built function do XD
 {
  num = num*10+(s[i]-'0');
 }

string number to integer number C++

stoi(string_number) ;

string to int c++

#include <iostream>
#include <string>

// namespace because why not
namespace dstd
{
    int StringtoInt(std::string str)
    {
        int multiplier = 1;
        int sum = 0;
        for(int i = str.size() - 1;i >= 0; i--)
        {
            switch(str[i])
            {
                case '0':
                sum += 0;
                break;
                case '1':
                sum += 1 * multiplier;
                break;
                case '2':
                sum += 2 * multiplier;
                break;
                case '3':
                sum += 3 * multiplier;
                break;
                case '4':
                sum += 4 * multiplier;
                break;
                case '5':
                sum += 5 * multiplier;
                break;
                case '6':
                sum += 6 * multiplier;
                break;
                case '7':
                sum += 7 * multiplier;
                break;
                case '8':
                sum += 8 * multiplier;
                break;
                case '9':
                sum += 9 * multiplier;
                break;
                case '-':
                sum *= -1;
                break;
                case ' ':
                continue;
                case 
            }
            multiplier *= 10;
        }

        return sum;
    }
}

int main()
{
  //just an example of how to use the function
    int a = dstd::StringtoInt("1992");
  	std::cout<<a<<'
';
}

Converting Strings to Numbers in C/C++

Converting Strings to Numbers
1. Using string Stream 
2. Using stoi()
3. Using atoi()

To see more example please click the source link.