Create a string which will use a previous integer as the size

Question

why it's not possible to create an char array in this way?

int main() 
{
    int len;

    cin>>len;
    char input_str[len];

    cin>>input_str;
    cout<<input_str;


    return 0;
}

C added this feature; C++ didn't and recommends the use of STL templates, such as `std::string`. — MicroVirus, Jul 04 '15 at 20:56
possible duplicate of [Variable length arrays in C++?](http://stackoverflow.com/questions/1887097/variable-length-arrays-in-c) — Steve Fallows, Jul 04 '15 at 21:04

score 0 · Answer 1 · answered Jul 03 '15 at 01:14

You cannot use a static array without knowing the size of the array at runtime. Instead you can use a pointer and use either "malloc" or "new" to allocate memory for the array dynamically:

1) First check that the user has entered a valid int

2) Once you have a valid int to work with, you can use...

char *input_str = new char[len];

for C++ or if you have to stick with plain old C use ...

char *input_str = (char *)malloc(len * sizeof(char));

Create a string which will use a previous integer as the size

1 Answers1