Palindrome Checker in C++

A palindrome is a string that reads the same forward and backward. In this program, we will check if a given string is a palindrome using C++.

Program Explanation

The program works as follows:

1. Take input from the user as a string.
2. Remove any non-alphanumeric characters and convert the string to lowercase to ensure the check is case-insensitive and ignores punctuation.
3. Compare the cleaned string with its reverse to check if it’s a palindrome.

C++ Code

// Palindrome Checker in C++

#include <iostream>
#include <algorithm>
#include <cctype>
#include <string>

using namespace std;

/**
 * @brief Function to check if a given string is a palindrome.
 * @param str The input string to check.
 * @return true if the string is a palindrome, false otherwise.
 */
bool isPalindrome(const string& str) {
    string cleanedStr;
    
    // Remove non-alphanumeric characters and convert to lowercase
    for (char ch : str) {
        if (isalnum(ch)) {
            cleanedStr += tolower(ch);
        }
    }

    // Compare cleaned string with its reverse
    string reversedStr = cleanedStr;
    reverse(reversedStr.begin(), reversedStr.end());

    return cleanedStr == reversedStr;
}

int main() {
    string input;
    cout << "Enter a string: ";
    getline(cin, input);

    if (isPalindrome(input)) {
        cout << "The string is a palindrome." << endl;
    } else {
        cout << "The string is not a palindrome." << endl;
    }

    return 0;
}
    

Explanation of the Code

• Include Headers: The program includes necessary headers for input/output, string manipulation, and algorithms.

  #include <iostream>
  #include <algorithm>
  #include <cctype>
  #include <string>

• Namespace: Using the standard namespace for convenience.

  using namespace std;

• isPalindrome Function: This function checks if a given string is a palindrome.

  bool isPalindrome(const string& str) {
      string cleanedStr;
  
      // Remove non-alphanumeric characters and convert to lowercase
      for (char ch : str) {
          if (isalnum(ch)) {
              cleanedStr += tolower(ch);
          }
      }
  
      // Compare cleaned string with its reverse
      string reversedStr = cleanedStr;
      reverse(reversedStr.begin(), reversedStr.end());
  
      return cleanedStr == reversedStr;
  }

  This function takes the following steps:

  • Iterates over each character of the input string.
  • Checks if the character is alphanumeric using isalnum.
  • Converts the character to lowercase using tolower and appends it to cleanedStr.
  • Reverses cleanedStr and compares it with the original cleaned string.
• main Function: This is the entry point of the program.

  int main() {
      string input;
      cout << "Enter a string: ";
      getline(cin, input);
  
      if (isPalindrome(input)) {
          cout << "The string is a palindrome." << endl;
      } else {
          cout << "The string is not a palindrome." << endl;
      }
  
      return 0;
  }

  The main function:

  • Prompts the user to enter a string.
  • Calls the isPalindrome function to check if the string is a palindrome.
  • Outputs the result to the console.

Sample Output

Here is an example of the program in action:

Enter a string: A man, a plan, a canal, Panama
The string is a palindrome.

Enter a string: Hello, World!
The string is not a palindrome.