Strings in C++ (original) (raw)

Last Updated : 26 Apr, 2026

Strings in C++ are objects of the std::string class. They are used to represent and manipulate sequences of characters.

• Unlike C-style character arrays (char[]), std::string handles memory management automatically and provides a wide range of built-in functions for ease of use.
• Can automatically grow and shrink as you add or remove characters, unlike fixed-size C-style strings.
• You can easily access characters, join strings, compare them, extract substrings, and search within strings using built-in functions. C++ `

#include #include using namespace std;

int main() {

// Creating a string
string str = "Hello Geeks";

// Traversing using index
cout << "Using index: ";
for (int i = 0; i < str.size(); i++) {
    cout << str[i] ;
}
cout << endl;

// Traversing using range-based for loop
cout << "Using range-based for loop: ";
for (char ch : str) {
    cout << ch ;
}
cout << endl;

// Traversing using iterator
cout << "Using iterator: ";
for (auto it = str.begin(); it != str.end(); it++) {
    cout << *it ;
}
cout << endl;

return 0;

}

`

Output

Using index: Hello Geeks Using range-based for loop: Hello Geeks Using iterator: Hello Geeks

Syntax

The string container is defined as std::string class inside the header file.

string str;

where,

• **string: Class provided by STL to handle sequences of characters.
• **str: Name assigned to the string object.

Basic Operations in String

Basic operations on Strings are shown below:

Initializing a String

• Initialization of a string assigns characters to the string at the time of creation.
• A string can be initialized directly using = or constructor syntax with text inside quotes. C++ `

#include #include using namespace std;

int main() {

// Initializing a string directly
string str = "Hello Geeks";

// Printing the string
cout << str << endl;

return 0;

}

`

Accessing Characters

• Characters of a string can be accessed using the [] operator or the .at() function.
• Time complexity for accessing characters is O(1). C++ `

#include #include using namespace std;

int main() { string str = "Hello Geeks";

// Access using index operator []
cout << "First character: " << str[0] << endl;
cout << "Fifth character: " << str[4] << endl;

// Access using at()
cout << "Character at index 6: " << str.at(6) << endl;

return 0;

}

`

Output

First character: H Fifth character: o Character at index 6: G

String Length

• The number of characters in a string can be found using size() or length().
• Time complexity to find string length is O(1). C++ `

#include #include using namespace std;

int main() { string str = "Hello Geeks";

// Using size()
cout << "Length using size(): " << str.size() << endl;

// Using length()
cout << "Length using length(): " << str.length() << endl;

return 0;

}

`

Concatenation of Strings

• Strings can be joined using the + operator or the append() function.
• The + operator creates a new string, while append() modifies the existing string in place.
• Time complexity for concatenation is O(n+m), where n is the size of string and m is the size of the string to be concatenated. C++ `

#include #include using namespace std;

int main() { string str1 = "Hello"; string str2 = " Geeks";

// Using + operator
string result1 = str1 + str2;
cout << "Concatenation using + : " << result1 << endl;

// Using append() function
string result2 = str1;
result2.append(str2);
cout << "Concatenation using append(): " << result2 << endl;

return 0;

}

`

Output

Concatenation using + : Hello Geeks Concatenation using append(): Hello Geeks

Modifying a String

• Characters of a string can be added with .push_back(), removed with .pop_back(), or altered using .insert() and .erase().
• Time complexity for push/pop is O(1) and O(n) for insert/erase. C++ `

#include #include using namespace std;

int main() { string str = "Hello Geeks";

// Adding a character at the end
str.push_back('!');
cout << "After push_back: " << str << endl;

// Removing the last character
str.pop_back();
cout << "After pop_back: " << str << endl;

// Inserting a substring
str.insert(5, " C++");
cout << "After insert: " << str << endl;

// Erasing part of the string
str.erase(5, 4); 
cout << "After erase: " << str << endl;

return 0;

}

`

Output

After push_back: Hello Geeks! After pop_back: Hello Geeks After insert: Hello C++ Geeks After erase: Hello Geeks

Substring Extraction

• The .substr(pos,len) is used to extract a part of a string, where pos means the starting position and len means how many characters you want to copy.
• This function creates a new string containing the selected portion, starting at pos and copying len characters.
• Time complexity of extraction is O(len). C++ `

#include #include using namespace std;

int main() { string str = "Hello Geeks";

// Extract "Hello"
string sub1 = str.substr(0, 5);   
cout << "Substring 1: " << sub1 << endl;

// Extract "Geeks"
string sub2 = str.substr(6, 5);  
cout << "Substring 2: " << sub2 << endl;

return 0;

}

`

Output

Substring 1: Hello Substring 2: Geeks

Know more about Substring extraction in C++.

Searching in a String

• The find() function is used to search for a substring inside a string. If found, it returns the index (position) where the substring starts; if not, it returns a special value (npos).
• Time complexity to search is O(n*m), where n is the length of string and m is the substring length. C++ `

#include #include using namespace std;

int main() { string str = "Hello Geeks";

size_t pos = str.find("Geeks");  

if (pos < str.size()) {
    cout << "\"Geeks\" found at index: " << pos << endl;
}

return 0;

}

`

Output

"Geeks" found at index: 6

Learn more about find() in C++

C++ String Functions

C++ provides some inbuilt functions which are used for string manipulation, such as the strcpy() and strcat() functions for copying and concatenating strings. Some of them are:

These functions are discussed in this article in more detail - String Function in C++