Strings

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Data Structures and Algorithms (DSA) in C++: Strings

In C++, strings are sequences of characters represented by the std::string class from the Standard Template Library (STL). Strings in C++ are powerful and versatile, offering a wide range of operations and utilities for manipulating and working with text data efficiently. Here’s an overview of strings in C++:

Basics of C++ Strings

• Definition: A string in C++ is a sequence of characters stored as a contiguous array. It is represented by the std::string class, which provides a rich set of operations and utilities.

• Initialization: Strings can be initialized in various ways:

        std::string str1 = "Hello"; // Initialized with a literal
        std::string str2("World"); // Initialized with a constructor
        std::string str3 = str1 + " " + str2; // Concatenation
        
      

Accessing Characters: Characters in a string can be accessed using array notation or iterators:

        std::string str = "Hello";
        char firstChar = str[0]; // Accessing first character
      

Length: The length of a string can be obtained using the length() or size() member functions:

        std::string str = "Hello";
        int len = str.length(); // len = 5
      

Common Operations on Strings

• Concatenation: Combining two strings using the + operator or append() function.

        std::string str1 = "Hello";
        std::string str2 = "World";
        std::string result = str1 + " " + str2; // "Hello World"
      

Substring: Extracting a part of the string using substr() function.

        std::string str = "Hello World";
        std::string substr = str.substr(6, 5); // "World"
      

Searching: Searching for substrings or characters using find() or find_first_of() functions.

        std::string str = "Hello World";
        size_t found = str.find("World"); // found = 6
      

Modification: Modifying characters or sections of the string directly.

        std::string str = "Hello";
        str[0] = 'J'; // "Jello"
      

Example Usage

Example 1: Counting Occurrences of a Character

        #include 
          #include 
          
          int countOccurrences(const std::string& str, char target) {
              int count = 0;
              for (char ch : str) {
                  if (ch == target) {
                      count++;
                  }
              }
              return count;
          }
          
          int main() {
              std::string str = "Hello, World!";
              char target = 'l';
          
              int count = countOccurrences(str, target);
              std::cout << "Occurrences of '" << target << "': " << count << std::endl;
          
              return 0;
          }
      

Example 2: Checking Palindrome

        #include 
          #include 
          #include 
          
          bool isPalindrome(const std::string& str) {
              std::string reversed = str;
              std::reverse(reversed.begin(), reversed.end());
              return str == reversed;
          }
          
          int main() {
              std::string str = "madam";
          
              if (isPalindrome(str)) {
                  std::cout << str << " is a palindrome." << std::endl;
              } else {
                  std::cout << str << " is not a palindrome." << std::endl;
              }
          
              return 0;
          }
      

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