Possible Duplicate:
c++ converting string to int
I have the user input 9 numbers in sequence. I need to convert the string numbers to an int
string num;
int num_int, product[10];
cout << "enter numbers";
cin >> num;
for(int i =0; i<10; i++){
product[i] = num[i] * 5; //I need the int value of num*5
}
Why don't you just read immediately to an integer?
int num;
cin >> num;
You do not need to have two variables. It's usual in C++ to convert on the fly, in the input stream, without ever seeing the text as a string. So you can simply write:
int num;
std::vector< int > product( 10 );
std::cout << "enter number: ";
std::cin >> num;
...
Note that I've corrected the way you've declared the array as
well. You wouldn't normally use int product[10]; in C++.
(And you'd almost never define two variables on the same line,
even if the language allows it.)
The easiest way by far to convert to a string and back again is to use the conversion functions.
std::string s="56";
int i=std::stoi(s);
http://en.cppreference.com/w/cpp/string/basic_string/stol
and back
int i=56;
std::string s=std::to_string(i);
http://en.cppreference.com/w/cpp/string/basic_string/to_string
of course if you are reading input you might as well do it then and there too
int i;
std::cin >> i;
Here is a full sample:
//library you need to include
#include <sstream>
int main()
{
char* str = "1234";
std::stringstream s_str( str );
int i;
s_str >> i;
}
if you absolutely must use a std::string (for any other reason.. perhaps homework?) then you can use the std::stringstream object to convert it from a std::string to int.
std::stringstream strstream(num);
int iNum;
num >> iNum; //now iNum will have your integer
Alternatively, you can use the atoi function from C to help you with it
std::string st = "12345";
int i = atoi(st.c_str()); // and now, i will have the number 12345
So your program should look like:
vector<string> num;
string holder;
int num_int, product[10];
cout << "enter numbers";
for(int i = 0; i < 10; i++){
cin >> holder;
num.push_back(holder);
}
for(int i =0; i<10; i++){
product[i] = atoi(num[i].c_str()) * 5; //I need the int value of num*5
}
num[i]? That accesses just a single character fromnum.