C++ String Class and its Applications
The String class is available in C++. The character array is represented by the C string. The string class in C++ has a few different attributes. It contains several functions that can be utilised to do various jobs. In this tutorial, we will look at the String class's key characteristics.
The string class is part of the C++ library and provides significantly more capability than C-style strings. The length of a C++ string can be altered at runtime due to dynamic memory allocation, which is analogous to vectors. Because the string class is a container class, we can use an iterator to traverse over all of its characters, just like other containers like vector, set, and maps, but we usually use a simple for loop to iterate over the characters and index them using the [] operator.
The C++ string class includes a variety of functions for easily manipulating strings. The most useful ones are demonstrated in the code below.
C++ Program:
#include<iostream>
using namespace std;
int main ()
{
string strng ( "This is a string" );
cout << " String is: " << strng << endl;
string strng2 ( strng );
cout << " String is: " << strng2 << endl;
string strng3 ( 5, 'F' );
cout << " String is: "<< strng3 << endl;
string strng4 ( strng, 5, 10 );
cout << " String is: " << strng4 << endl;
string strng5 ( strng.begin (), strng.begin () + 7 );
cout << " String is: " << strng5 << endl;
}
Output:
String is: This is a string
String is: This is a string
String is: FFFFF
String is: is a strin
String is: This is
We'll now look at various String class operators. The fundamental operators are the assignment operator (=), the concatenate operator (+), and the index operator ([ ]). Let's look at some examples of these operators.
C++ Program:
#include<iostream>
using namespace std;
int main () {
string strng = "Hi ";
string strng2 = "Rohit";
string strng3, strng4;
strng3 = strng; //use assignment operator
cout << "The value of str3: " << strng3 << endl;
strng4 = strng + strng2; //concatenate two strings
cout << "The value of str4: " << strng4 << endl;
cout << "Character at position 1 of str: " << strng [1] << endl;
}
Output:
The value of str3: Hi
The value of str4: Hi Rohit
Character at position 1 of str: iFinally, let's look at some string methods. These routines are used to perform key string-related tasks. Let's look at how the functions work in the example code.
C++ Program:
#include<bits/stdc++.h>
using namespace std;
int main () {
string str1 = "Hello World!";
cout << "The String before clearing : " << str1 << endl;
str1.clear (); // clean the string
cout << "The String after clearing : " << str1 << endl;
str1 = "It is a string:";
cout << "The length of the String using size() and length() functions: " << str1.size() << " and " << str1.length() << endl;
cout << "The character at 1 position of the string is : " << str1.at(1) << endl;
cout << "First character of the string is : " << str1.front() << endl;
cout << "Last character of the string is : " << str1.back() << endl;
cout << "The string to C like character array: " << str1.c_str() << endl;
cout << "The string after appending some text in it : " << str1.append("ABCDEFGHIJ") << endl;
string string2 = "IT IS AN ANOTHER STRING";
cout << "The string after appending the text from string2 : " << str1.append(string2,0, 5) << endl;
// We use the find function to find the substring of the string
if ( str1.find("AN") != string::npos )
cout << "\"AN\" is found in the string at " << str1.find("AN") << " position" <<endl;
else
cout << "substring not found in the string" << endl;
cout << "The Substring of the length 3 from index 5: " <<str1.substr(5, 3) <<endl;
cout << "The String after erasing the 4 characters from index 5: " <<str1.erase(5, 4) << endl;
cout << "Replace the 7 characters from index 3: " <<str1.replace(3, 7, "C++Programming");
}
Output:
The String before clearing : Hello World!
The String after clearing :
The length of the String using size() and length() functions: 15 and 15
The character at 1 position of the string is : t
First character of the string is : I
Last character of the string is : :
The string to C like character array: It is a string:
The string after appending some text in it : It is a string:ABCDEFGHIJ
The string after appending the text from string2 : It is a string:ABCDEFGHIJIT IS
substring not found in the string
The Substring of the length 3 from index 5: a
The String after erasing the 4 characters from index 5: It istring:ABCDEFGHIJIT IS
Replace the 7 characters from index 3: It C++Programming:ABCDEFGHIJIT IS