C++ Recursion: Checking palindrome strings using recursive function

Last update on December 20 2024 12:25:17 (UTC/GMT +8 hours)

Write a C++ program to implement a recursive function to check if a given string is a palindrome.

A palindrome is a word, number, phrase, or other sequence of symbols that reads the same backwards as forwards, such as madam or racecar, the date and time 12/21/33 12:21, and the sentence: "A man, a plan, a canal – Panama".

Sample Solution:

C Code:

// Recursive function to check if a string is a palindrome
#include <iostream> // Including the Input/Output Stream Library
#include <string>   // Including the String Library
#include <algorithm> // Including the Algorithm Library

// Recursive function to check if a string is a palindrome
bool isPalindrome(const std::string & text, int start, int end) {
  // Base case: when start >= end, the string is a palindrome
  if (start >= end)
    return true;

  // Recursive case: check if the characters at start and end indices are equal,
  // and recursively check the remaining characters
  if (text[start] != text[end])
    return false;

  return isPalindrome(text, start + 1, end - 1);
}

int main() {
  std::string text; // Declaring a variable to store the input string

  std::cout << "Input a string: ";
  std::getline(std::cin, text); // Taking input for the string

  // Remove any spaces from the input string
  text.erase(std::remove(text.begin(), text.end(), ' '), text.end());

  // Check if the string is a palindrome using recursion
  bool palindrome = isPalindrome(text, 0, text.length() - 1); // Checking if the input string is a palindrome

  // Display the result
  if (palindrome)
    std::cout << "The string is a palindrome." << std::endl;
  else
    std::cout << "The string is not a palindrome." << std::endl;

  return 0; // Returning 0 to indicate successful execution of the program
}

Sample Output:

Input a string: madam
The string is a palindrome.

Input a string: abc
The string is not a palindrome.

Flowchart:

CPP Code Editor:

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