Convert char* to string in C++

There are three ways to convert char* into string in C++.

1. Using the “=” operator
2. Using the string constructor
3. Using the assign function

1. Using the “=” operator

Using the assignment operator, each character of the char pointer array will get assigned to its corresponding index position in the string.

C++

// C++ Program to demonstrate the conversion
// of char* to string using '='
#include <iostream>
using namespace std;

int main()
{
    // declaration of char*
    const char* ch = "Welcome to GeeksForGeeks";
    string s = ch;
    cout << s;
    return 0;
}

Output

Welcome to GeeksForGeeks

2. Using string constructor

The string constructor accepts char* as an argument and implicitly changes it to string.

C++

// C++ Program to demonstrate the conversion
// of char* to string using string constructor
#include <iostream>
using namespace std;

int main()
{
    const char* ch = "Welcome to GeeksForGeeks";
    string s(ch);
    cout << s;
    return 0;
}

Output

Welcome to GeeksForGeeks

3. Using the assign function

It accepts two arguments, starting pointer and ending pointer, and converts the char pointer array into a string.

C++

// C++ Program to demonstrate the conversion
// of char* to string using assign function
#include <iostream>
using namespace std;

int main()
{
    const char* ch = "Welcome to GeeksForGeeks";
    string str;

    // 24 is the size of ch
    str.assign(ch, ch + 24);
    cout << str;
    return 0;
}

Output

Welcome to GeeksForGeeks

Time complexity: O(N), as time complexity of assign() is O(N) where N is the size of the new string
Auxiliary space: O(1).