How to do an array of the same size of a string?

Question

I tried this way :
string a;
cin >> a ;
char b [a.lenght ()];
including string libraries, but i cant' make an array not knowin is size before.
Can someone help me?

Answer 1

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

int main ()
{
string a;
cin >> a;

char b[strlen(a.c_str())];

return 0;
}

// tested and working.
// you may find array size using
// cout << sizeof(b)/sizeof(b[0]);

Answer 2

char b[a.length()];
// fix the spelling of length

Answer 3

char b [a.length () + 1]; // +1 for null character '\0' in case of char array.