We covered the fundamentals of String Class in C++ in our previous post. In this post, we are going to cover the several operations and functionalities that we can perform on the String type. There are several member functions that are available in string class in C++ which is veryful for solving string related coding problems.
Here we are going to discuss all the string member functions available in C++ programming language with real example and code implementation.
Example C++ Code:
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Example C++ Code:
Output:
Example C++ Code:
Output:
In the above code, when we use the reverse iterator to print our string then it prints the string in reverse order because begin() points to the end of the string to it start printing in reverse order.
Example C++ Code:Output:In the above code, the copy() function return the character array and with null character at the end so we need to append it sepeararately or it might cause unexpected error. The substr() function help to capture substring and usually required two argument (starting position and size of substring) but if you don't provide the size of substring then it will capture from starting position till end of the string.
String empty() function in C++.
| String Function | Definition |
|---|---|
| empty() | This function is used to check if a string is empty or not. It returns 1 if a string is empty else returns 0 if a string is not empty. |
/*C++ program to show the working of empty() function */ #include<iostream> #include<string> using namespace std; int main(){ string str; //taking input from user cout<<"Enter a string: "; getline(cin, str); //checking string is empty or not if(!str.empty()){ cout<<"The string is: "<<str<<endl; } else{ cout<<"The string is empty!"<<endl; } return 0; }
Enter a string: The string is empty! Enter a string: Algolesson The string is: Algolesson
In the output of the above code, you can see that when I enter nothing as an input, the empty() function checks the string and executes the else part saying, "The string is empty!". You have also noticed one getline() function that takes input from the user.
String Modifier functions in C++.
| String Function | Definition |
|---|---|
| push_back() | This function is used to add a character at the end of the string. |
| pop_back() | This function is used to delete the last character from the string. |
| insert() | This function is used to insert additional characters into the string. |
| erase() | This function is used to remove the part of the string which reduce the size of the string. |
Example C++ Code:
/*C++ program to show the working of erase() insert(), push_back() and pop_back() function */ #include<iostream> #include<string> using namespace std; int main(){ string str; //taking input from the user cout<<"Enter a string: "; getline(cin, str); cout<<"The string is: "<<str<<endl; //adding a char at the end of the string str.push_back('s'); cout<<"String after push_back() operation: "<<str<<endl; //removing a char from the end of the string str.pop_back(); cout<<"String after pop_back() operation: "<<str<<endl;
string str1 = "Rose is a "; str.insert(0, str1); cout<<"String after insert operation: "<<str<<endl; str.erase(10, 10); cout<<"String after erase operation: "<<str<<endl;return 0; }
Enter a string: Beautiful Flower The string is: Beautiful Flower String after push_back() operation: Beautiful Flowers String after pop_back() operation: Beautiful Flower
String after insert operation: Rose is a Beautiful FlowerString after erase operation: Rose is a FlowerIf you are already working with string then you probably know the functionality of getline() function. In the above code, push_back('s') adds one s character at the end of our string and the pop_back() function removes that end 's' character.
String Capacity functions in C++.
| String Function | Definition |
|---|---|
| capacity() | This function is used to return the capacity allocated to the string which can be equal to more than the length of the string. |
| length() | This function is used to check the length of the string. |
| resize() | This function is used to change the size of the current string. The size of the string can be increased or decreased based on demand. |
| shrink_to_fit() | This function is used to decrease the capacity of the string to fit its size. It makes string capacity equal to string size. |
| size() | This function is used to find the length of the string which also indicates the number of characters present in the string. |
- The size() functional and length() function return the same value always.
/*C++ program to show the working of resize(), capacity() and shrink_to_fit() function */ #include<iostream> #include<string> using namespace std; int main(){ string str; //taking input from user cout<<"Enter a string: "; getline(cin, str); cout<<"The string is: "<<str<<endl; str.resize(7); cout<<"String after resize operation: "<<str<<endl; cout<<"The capacity of the string is: "<<str.capacity()<<endl; cout<<"The length of the string is: "<<str.length()<<endl; str.shrink_to_fit(); cout<<"The capacity of the string after shrink: "<<str.capacity()<<endl;
cout<<"The size of the string is: "<<str.size()<<endl;return 0; }
Enter a string: Welcome to Algolesson The string is: Welcome to Algolesson String after resize operation: Welcome The capacity of the string is: 30 The length of the string is: 7 The capacity of the string after shrink: 15
The size of the string is: 7In the above, code you can see that number of characters present in the input string was 21 and after resizing the string to 7 it contains only 7 characters but the capacity of the string was still 30 and even tho the length of the string showing is 7 so after performing shrink operation to free unwanted memory the capacity reduced to 15.
String Iterator Functions in C++.
| String Function | Definition |
|---|---|
| begin() | This function is used to return an iterator to the beginning of the string. |
| end() | This function is used to return an iterator to the end of the string. |
| rbegin() | This function is used to return a reverse iterator pointing at the end of the string. |
| rend() | This function is used to return a reverse iterator pointing at the beginning of the string. |
/*C++ program to show the working of begin(), end() rbegin() and rend() function */ #include<iostream> #include<string> using namespace std; int main(){ string str = "Algolesson"; std::string::iterator it; cout<<"Print String using forward iterator: "; for(it = str.begin(); it != str.end(); it++) cout<<*it; cout<<endl; std::string::reverse_iterator rit; cout<<"Print String using reverse iterator: "; for(rit = str.rbegin(); rit != str.rend(); rit++) cout<<*rit; return 0; }
Print String using forward iterator: Algolesson Print String using reverse iterator: nosseloglA
String Operation Functions in C++.
| String Function | Definition |
|---|---|
| copy() | This function is used to copy a sequence of characters from the string. This function returns a char array and the function required three arguments, the name of the char array, the length of the string to be copied, and the starting position of copying. |
| find() | This function is used to find content in the string. It can contain two arguments,
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| substr() | This function is used to generate a substring of the string. It contain two argument,
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| compare() | This function is used to compare two strings and return 0 if both are equal. |
/*C++ program to show the working of copy(), find() substr() and compare() function */ #include<bits/stdc++.h> #include<iostream> #include<string> using namespace std; int main(){ string str = "Coding is Fun"; string str1 = "Programming is Fun Coding is Fun"; string str2 = "Fun"; //char array of size 20 char copystr[20]; int length = str1.copy(copystr, 11, 0); copystr[length] = '\0'; cout<<"The copied character array is: "<<copystr<<endl; int found = str1.find(str2); cout<<"The First occurrence of str2 at: "<<found<<endl; found = str1.find(str2, found+1); cout<<"The Second occurrence of str2 at: "<<found<<endl; string str3 = str1.substr(19, 6); cout<<"The First substring is: "<<str3<<endl; str3 = str1.substr(19); cout<<"The Second substring is: "<<str3<<endl; if(str.compare(str3) == 0) cout<<"Both strings are equal."<<endl; return 0; }
The copied character array is: Programming The first occurrence of str2 at: 15 The Second occurrence of str2 at: 29 The First substring is: Coding The Second substring is: Coding is Fun Both strings are equal.
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