1. Introduction
2. String object in C++
3. String relational operators
4. String modification functions
5. String attribute functions
6. Accessing string elements
7. Comparing string functions
1. Introduction
String is a sequence of characters. Every string should be terminated by NULL character ‘\0’. In C style, an extra space need to be allocated to hold a NULL value.
C style string:
char website_name [21] = “prodevelopertutorial”; C++ provides “string” object that makes string manipulation easy.
2. String object in C++
“string” is the keyword used to declare a string variable.
Below are various examples on how to use strings:
string text; //Creates an empty string
string language("c++"); //assigns "c++" to the variable language
string_1 = string_2 //assign value of string_2 to string_1
string_1 = "c++" + "tutorials" // string concatenation Example on string usage in C++
/*
* File : strings_example.cpp
* Author : ajay.thousand@gmail.com
* Copyright: @ prodevelopertutorial.com
*/
#include<iostream>
#include<string>
using namespace std;
int main()
{
string string_1 = "c++";
string string_2(" prodevelopertutorial");
string string_3;
cout<<"The string_1 is "<<string_1<<endl;
cout<<"The string_2 is "<<string_2<<endl;
//string concatenation
string_1 += string_2;
cout<<"The string_1 after concatenation is \""<<string_1<<"\""<<endl;
//string assignment
string_3 = string_2;
cout<<"The string_3 after assignment is "<<string_3<<endl;
return 0;
}
Output:
The string_1 is c++
The string_2 is prodevelopertutorial
The string_1 after concatenation is "c++ prodevelopertutorial"
The string_3 after assignment is prodevelopertutorial3. String relational operators
We can use relational operators (shown below) to compare 2 string are same or not.
== operator checks if both strings are same
> checks if string_1 is greater than string_2
Example of relational operators:
/*
* File : strings_relational_operator_example.cpp
* Author : ajay.thousand@gmail.com
* Copyright: @ prodevelopertutorial.com
*/
#include<iostream>
#include<string>
using namespace std;
int main()
{
string string_1 = "c++";
string string_2("c++");
string string_3 = "C++";
cout<<"The string_1 is = "<<string_1<< " and string_2 is = "<<string_2<<" and string_1 == string_2 value is = "<<(string_1 == string_2) <<endl;
cout<<"The string_1 is = "<<string_1<< " and string_3 is = "<<string_3<<" and string_1 == string_3 value is = "<<(string_1 == string_3) <<endl;
cout<<"The string_1 is = "<<string_1<< " and string_2 is = "<<string_2<<" and string_1 > string_2 value is = "<<(string_1 > string_2) <<endl;
cout<<"The string_1 is = "<<string_1<< " and string_3 is = "<<string_3<<" and string_1 > string_3 value is = "<<(string_1 > string_3) <<endl;
return 0;
}Output:
The string_1 is = c++ and string_2 is = c++ and string_1 == string_2 value is = 1
The string_1 is = c++ and string_3 is = C++ and string_1 == string_3 value is = 0
The string_1 is = c++ and string_2 is = c++ and string_1 > string_2 value is = 0
The string_1 is = c++ and string_3 is = C++ and string_1 > string_3 value is = 14. String modification functions
Below are the functions used to modify strings.
1. insert() function is used to insert a string at a specified position.
Syntax:
string_1.insert(<position>, <string_to_insert>);2. erase() function is used to erase the specified characters.
Syntax:
string_1.insert(<position_start>, <position_end>);3. replace() function is used to replace the specified characters.
Syntax:
string_1.insert(<position_start>, <position_end>, <string_2>);4. append() function is used to append another string at the end of first string.
Syntax:
string_1.append(string_2);Example for string Modification function:
/*
* File : strings_modification_example.cpp
* Author : ajay.thousand@gmail.com
* Copyright: @ prodevelopertutorial.com
*/
#include<iostream>
#include<string>
using namespace std;
int main()
{
string string_1 = "c++ ";
string string_2 = "Tutorial";
string string_3 = "prodevelopertutorial.com";
string string_4 = "Tutorial on prodevelopertutorial";
string string_5 = "c++ ";
cout<<"The string_1 is = "<<string_1<< " and string_2 is = "<<string_2<<" and string_1.insert(4, string_2) value is = "<<(string_1.insert(4, string_2)) <<endl;
cout<<"The string_3 is = "<<string_3<< " and string_3.erase(20, 24) value is = "<<(string_3.erase(20, 24)) <<endl;
cout<<"The string_3 is = "<<string_3<< " and string_3.replace(3, 9, \"DEVELOPER\") value is = "<<(string_3.replace(3, 9, "DEVELOPER")) <<endl;
cout<<"The string_5 is = "<<string_5<< " and string_4 is = "<<string_4<<" and string_5.append(string_4) value is = "<<(string_5.append(string_4)) <<endl;
return 0;
}Output:
The string_1 is = c++ and string_2 is = Tutorial and string_1.insert(4, string_2) value is = c++ Tutorial
The string_3 is = prodevelopertutorial.com and string_3.erase(20, 24) value is = prodevelopertutorial
The string_3 is = prodevelopertutorial and string_3.replace(3, 9, “DEVELOPER”) value is = proDEVELOPERtutorial
The string_5 is = c++ and string_4 is = Tutorial on prodevelopertutorial and string_5.append(string_4) value is = c++ Tutorial on prodevelopertutorial
5. String attribute functions
Below are the functions used to get string attributes.
1. size() function is used to get the size of string object. It gives the number of bytes occupied by that string object.
Syntax:
string_1.size()2. length() function is used to get the length of string object. It gives the number of characters present in that string object.
Syntax:
string_1.length()3. capacity() function is used to get the capacity of string object.
Syntax:
string_1.capacity()4. max_size() function is used to get the maximum size of string object.
Syntax:
string_1.max_size()Example for string attribute functions:
/*
* File : strings_attributes_example.cpp
* Author : ajay.thousand@gmail.com
* Copyright: @ prodevelopertutorial.com
*/
#include<iostream>
#include<string>
using namespace std;
int main()
{
string string_1;
cout<<"The value of string_1 is = "<<string_1<<" and size of string_1 is = "<<string_1.size()<<endl;
string_1 = "C++";
cout<<"The value of string_1 is = "<<string_1<<" and size of string_1 is = "<<string_1.size()<<endl<<endl;
string string_2;
cout<<"The value of string_2 is = "<<string_2<<" and length of string_2 is = "<<string_2.length()<<endl;
string_2 = "C++";
cout<<"The value of string_2 is = "<<string_2<<" and length of string_2 is = "<<string_2.length()<<endl<<endl;
string string_3;
cout<<"The value of string_3 is = "<<string_3<<" and capacity of string_3 is = "<<string_3.capacity()<<endl;
string_3 = "C++";
cout<<"The value of string_3 is = "<<string_3<<" and capacity of string_3 is = "<<string_3.capacity()<<endl<<endl;
string string_4;
cout<<"The value of string_4 is = "<<string_4<<" and max_size of string_4 is = "<<string_4.max_size()<<endl;
return 0;
}
Output:
The value of string_1 is = and size of string_1 is = 0
The value of string_1 is = C++ and size of string_1 is = 3
The value of string_2 is = and length of string_2 is = 0
The value of string_2 is = C++ and length of string_2 is = 3
The value of string_3 is = and capacity of string_3 is = 22
The value of string_3 is = C++ and capacity of string_3 is = 22
The value of string_4 is = and max_size of string_4 is = 184467440737095515996. Accessing string elements
1. at(): function is used to get the character at that index.
Example:
string_1 = “c++”
string_1.at(0) will return “c”
2. substr() function is used to get the substring from “start_index” to “end_index”.
Example: string_1. substr (2, 4)
3. find() function is used to check if a “sub string” is present in the “string” or not.
Example: string_1. find (“hi”)
4. find_first_of() : it is used to find the first occurrence of the given character.
Example: string_1. find_first_of (“/”)
5. find_last_of() : it is used to find the last occurrence of the given character.
Example: string_1. find_last_of (“/”)
Example of string accessing:
/*
* File : accessing_strings_example.cpp
* Copyright: @ prodevelopertutorial.com
*/
#include<iostream>
#include<string>
using namespace std;
int main()
{
string string_1 = "prodevelopertutorial";
cout<<"The value of string_1 is = "<<string_1<<" and the character at 2 is = "<<string_1.at(2)<<endl;
string string_2 = "c++ tutorial at prodevelopertutorial";
cout<<"The value of string_2 is = "<<string_2<<" and find(\" tutorial\") is = "<<string_1.find("tutorial")<<endl;
cout<<"The value of string_1 is = "<<string_1<<" and substr(3, 11) is = "<<string_1.substr(3, 11)<<endl;
string string_3 = "a/b/c";
cout<<"The value of string_3 is = "<<string_3<<" and find_first_of(\"/\") is = "<<string_3.find_first_of("/")<<endl;
cout<<"The value of string_3 is = "<<string_3<<" and find_last_of(\"/\") is = "<<string_3.find_last_of("/")<<endl;
return 0;
}
Output:
The value of string_1 is = prodevelopertutorial and the character at 2 is = o
The value of string_2 is = c++ tutorial at prodevelopertutorial and find(” tutorial”) is = 12
The value of string_1 is = prodevelopertutorial and substr(3, 11) is = developertu
The value of string_3 is = a/b/c and find_first_of(“/”) is = 1
The value of string_3 is = a/b/c and find_last_of(“/”) is = 3
7. Comparing string functions
1. compare() function is used to compare 2 strings.
2. swap() function is used to swap 2 strings.
Example:
/*
* File : compare_and_swap_strings_example.cpp
* Copyright: @ prodevelopertutorial.com
*/
#include<iostream>
#include<string>
using namespace std;
int main()
{
string string_1 = "prodevelopertutorial";
string string_2 = "prodevelopertutorial";
string string_3 = "Prodevelopertutorial";
cout<<"The string_1 is = "<<string_1<< " and string_2 is = "<<string_2<<" and string_1.compare( string_2) value is = "<<(string_1.compare( string_2)) <<endl;
cout<<"The string_1 is = "<<string_1<< " and string_3 is = "<<string_3<<" and string_1.compare( string_3) value is = "<<(string_1.compare( string_3)) <<endl;
string string_4 = " c++ tutorial";
cout<<"The string_1 is = "<<string_1<< " and string_4 is = "<<string_4<<endl;
string_1.swap(string_4);
cout<<"After swap"<<endl;
cout<<"The string_1 is = "<<string_1<< " and string_4 is = "<<string_4<<endl;
return 0;
}Output:
The string_1 is = prodevelopertutorial and string_2 is = prodevelopertutorial and string_1.compare( string_2) value is = 0
The string_1 is = prodevelopertutorial and string_3 is = Prodevelopertutorial and string_1.compare( string_3) value is = 32
The string_1 is = prodevelopertutorial and string_4 is = c++ tutorial
After swap
The string_1 is = c++ tutorial and string_4 is = prodevelopertutorial