Many of us have encountered error ‘cannot convert std::string to char[] or char* data type’.
Examples:
Input : string s = "geeksforgeeks" ;
Output : char s[] = { 'g', 'e', 'e', 'k', 's', 'f', 'o',
'r', 'g', 'e', 'e', 'k', 's' } ;
Input : string s = "coding" ;
Output : char s[] = { 'c', 'o', 'd', 'i', 'n', 'g' } ;
Method 1
A way to do this is to copy the contents of the string to char array. This can be done with the help of c_str() and strcpy() function.
The c_str() function is used to return a pointer to an array that contains a null terminated sequence of character representing the current value of the string.
Syntax:
const char* c_str() const ;
If there is an exception thrown then there are no changes in the string. But when we need to find or access the individual elements then we copy it to a char array using strcpy() function. After copying it, we can use it just like a simple array.
The length of the char array taken should not be less than the length of input string.
CPP
// CPP program to convert string// to char array#include <bits/stdc++.h>using namespace std;// driver codeint main(){ // assigning value to string s string s = "geeksforgeeks"; int n = s.length(); // declaring character array char char_array[n + 1]; // copying the contents of the // string to char array strcpy(char_array, s.c_str()); for (int i = 0; i < n; i++) cout << char_array[i]; return 0;} |
Output:
geeksforgeeks
Method 2:
CPP
// CPP program to convert string// to char array#include <iostream>#include <string.h>using namespace std;// driver codeint main(){ // assigning value to string s string s("geeksforgeeks"); // declaring character array : p char p[s.length()]; int i; for (i = 0; i < sizeof(p); i++) { p[i] = s[i]; cout << p[i]; } return 0;} |
Output:
geeksforgeeks
Method 3:
This is the simplest ad most efficient one. We can directly assign the address of 1st character of the string to a pointer to char. This should be the preferred method unless your logic needs a copy of the string.
C++14
// CPP program for the above approach#include <cstring>#include <iostream>#include <string>using namespace std;// Driver Codeint main(){ char* char_arr; string str_obj("GeeksForGeeks"); char_arr = &str;_obj[0]; cout << char_arr; return 0;} |
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