c++ - How can I transform a user-defined string into an integer -

i ask user input string, let's input "abc" or"def"

then, want set integer = 1 if abc entered , 2 if def entered.

if else entered, want invalid value.

so @ end, i'll have integer assigned 1 or 2 if valid value entered.

#include<iostream> #include<string> #include<sstream> using namespace std;  int main() {      string input = "";  // how string/sentence spaces cout << "please enter valid sentence (with spaces):\n>"; getline(cin, input); cout << ".\n" << "you entered: " << input << endl << endl;  int m if(input = abc)      return 0; } 

#include <iostream> #include <map> #include <string> #include <initializer_list>  using namespace std;  int main() {     const std::map<std::string, int> lookuptable = { {"abc", 1}, {"def", 2} };     string input = "";     int m;      while(true) {         cout << "please enter valid sentence (with spaces):\n>";         getline(cin, input);         std::map<std::string, int>::const_iterator = lookuptable.find(input);         if (it != lookuptable.end()) {             m = it->second;             break;         }     }      cout << "you entered: " << input << endl << endl;     cout << "m = " << m << endl; } 

second solution if want m const. assumes compiler supports lambda functions:

#include <iostream> #include <map> #include <string> #include <initializer_list>  using namespace std;  int main() {     const std::map<std::string, int> lookuptable = { {"abc", 1}, {"def", 2} };     string input = "";     const int m = [&]() {         while(true) {             cout << "please enter valid sentence (with spaces):\n>";             getline(cin, input);             std::map<std::string, int>::const_iterator = lookuptable.find(input);             if (it != lookuptable.end())                 return it->second;         }     }();      cout << "you entered: " << input << endl << endl;     cout << "m = " << m << endl; } 

if compiler not support above map initialization can use instead:

#include <iostream> #include <map> #include <string>  using namespace std;  std::map<std::string, int> initializemap() {     std::map<std::string, int> map;     map["abc"] = 1;     map["def"] = 2;     // add whatever else here     return map; }  int main() {     const std::map<std::string, int> lookuptable = initializemap();     string input = "";     int m;      while(true) {         cout << "please enter valid sentence (with spaces):\n>";         getline(cin, input);         std::map<std::string, int>::const_iterator = lookuptable.find(input);         if (it != lookuptable.end()) {             m = it->second;             break;         }     }      cout << "you entered: " << input << endl << endl;     cout << "m = " << m << endl; }