C++ Strings

A string is a sequence of characters surrounded by double quotes. The C++ programming language supperts the following two types of string concepts.

• String as character array
• String as object of string class

String as character array

In C++, a string may define as a character array. A character array is simply an array of characters that is terminated by a null character "\0".

#include <iostream>

using namespace std;

int main()
{
    char name[30] = {'R', 'a', 'm', 'a'};   // string as an array

    cout << "Hello, " << name << endl;

    return 0;
}

String as object of string class

The C++ standard library provides a built-in class string. The string class allows us to create an object that holds a sequence of characters - string.

#include <iostream>

using namespace std;

int main()
{
    string name = "Rama";   // string as an object

    cout << "Hello, " << name << endl;  // Accessing hole string

    cout << name[2] << endl;    // Accessing a character from string

    name[2] = 'n';  // Changing a character at index 2

    cout << "Hello, " << name << endl;

    return 0;
}

String handling functions in C++

The C++ has a standard library header file string.h. The string.h provides various built-in functions to work with string values.

• strcpy(string s1, string s2)
  - Used to copy string s2 into string s1
• strcat(string s1, string s2)
  - Used to perform the concatination of two strings
• strlen(string s)
  - Used to find the length of a string (total number of characters)
• strchr(string s, char ch)
  - Returns a pointer the first occurance of the given character in the string s.
• strstr(string s1, string s2)
  - Returns a pointer the first occurance of the string s2 in the string s1.
• strcmp(string s1, string s2)
  - Compares both string s1 and string s2 and returns 0 if both are the same; less than 0 if s1<s2; greater than 0 if s1>s2.

---

• int capacity(string s)
  - It returns the capacity allocated to the string s, which can be equal to or more than the size of the string.
• swap(string s)
  - It returns the capacity allocated to the string s, which can be equal to or more than the size of the string.
• resize(int newSize)
  - It changes the size of string, the size can be increased or decreased.
• shrink_to_fit()
  - It decreases the capacity of the string and makes it equal to the minimum capacity of the string.

Example

#include <iostream>

using namespace std;

int main()
{
    string name = "Rama";   // string as an object
    string message = "Good Morning";

    cout << "Length of the name => " << name.length() << endl;

    cout << "Capacity of the message => " << name.capacity() << endl;

    cout << "Before swap => name = " << name << ", message = " << message << endl;
    message.swap(name);

    cout << "After swap => name = " << name << ", message = " << message << endl;

    return 0;
}

Output