Contents
Strings
C++ Strings Overview
C++ offers two primary ways to handle strings: traditional C-style character arrays and the std::string class from the standard library, which provides a more flexible, dynamic approach.
1. C-Style Strings: C-style strings are simple character arrays ending with a null character ('\0'), inherited from the C language. They are efficient but lack the advanced features of the std::string class.
Example:
#include <iostream>
using namespace std;
int main() {
char s[] = "Programming";
cout << s << endl;
return 0;
}
Output:
Programming
2. std::string Class : The std::string class, part of the <string> library, introduces numerous advantages over C-style strings, such as dynamic sizing and various member functions for easy manipulation.
#include <iostream>
using namespace std;
int main() {
string str("Hello, C++");
cout << str;
return 0;
}
Output:
Hello, C++
Defining Strings with Repeating Characters
To define strings with repeated characters:
Example:
#include <iostream>
using namespace std;
int main() {
string str(4, 'A');
cout << str;
return 0;
}
Output:
AAAA
Methods for Taking String Input
1. Using cin
2. Using getline
3. Using stringstream
1. Using cin: The simplest method is to use cin with the extraction operator (>>), which reads input until a space is encountered.
Example:
#include <iostream>
using namespace std;
int main() {
string s;
cout << "Enter a word: ";
cin >> s;
cout << "Entered word: " << s << endl;
return 0;
}
Output:
Enter a word: Hello
Entered word: Hello
2. Using getline: The getline() function reads an entire line of input, including spaces.
Example:
#include <iostream>
using namespace std;
int main() {
string s;
cout << "Enter a sentence: ";
getline(cin, s);
cout << "Entered sentence: " << s << endl;
return 0;
}
Output:
Enter a sentence: C++ is powerful!
Entered sentence: C++ is powerful!
String Functions in C++
Common functions for manipulating std::string objects include:
length()swap()size()resize()find()push_back()pop_back()clear()
Example of Basic String Functions:
Length: 9
After push_back: Developers
After pop_back: Developer
After clear: String is empty
Iterators for String Traversal
C++ provides iterators for traversing strings, including forward and reverse iterators.
Example:
#include <iostream>
using namespace std;
int main() {
string s = "Coding";
cout << "Forward: ";
for (auto itr = s.begin(); itr != s.end(); ++itr) {
cout << *itr;
}
cout << endl;
cout << "Reverse: ";
for (auto ritr = s.rbegin(); ritr != s.rend(); ++ritr) {
cout << *ritr;
}
cout << endl;
return 0;
}
Output:
Forward: Coding
Reverse: gnidoC
String Capacity Functions
Capacity functions control a string’s memory allocation.
1. length(): Returns the string’s length.
2. capacity(): Returns the memory allocated.
3. resize(): Changes the string size.
4. shrink_to_fit(): Reduces allocated capacity to the minimum size.
Example:
#include <iostream>
using namespace std;
int main() {
string s = "Optimize";
cout << "Initial length: " << s.length() << endl;
cout << "Initial capacity: " << s.capacity() << endl;
s.resize(5);
cout << "After resize: " << s << endl;
s.shrink_to_fit();
cout << "Capacity after shrink_to_fit: " << s.capacity() << endl;
return 0;
}
Output:
Initial length: 8
Initial capacity: 15
After resize: Optim
Capacity after shrink_to_fit: 5