Question

C++ A palindrome is a string that reads the same backward as forward. For example, the words mom, dad, madam and radar are all palindromes. Write a class Pstring that is derived from the STL string class. The Pstring class adds a member functionbool isPalindrome( )that determines whether the string is a palindrome. Include a constructor that takes an STL string object as parameter and passes it to the string base class constructor. Test your class by having a main program that asks the user to enter a string. The program uses the string to initialize a Pstring object and then calls isPalindrome()to determine whether the string entered is a palindrome.You may find it useful to use the subscript operator [] of the string class: If str is a string object and k is an integer, then str[k] returns the character at position k in the string.

Answer 1

Palindrome_Testing.cpp

#include <string>
#include <iostream>
#include "Pstring.h"
using namespace std;

int main()
{
   string test_str;
   //get the input from the user
   cout << "Enter the string to test with no spaces: ";
   getline(cin, test_str);
   system("cls");

   Pstring str(test_str);
   //display the message whether the string is a palindrome
   if (str.isPalindrome())
       cout << "Yes, this string is a palindrome!";
   else
       cout << "No, this string is not a palindrome.";

   cout << endl << endl;
   system("pause");
    return 0;
}

Pstring.cpp

#include <iostream>
#include "Pstring.h"
#include <string>
using namespace std;

/*
This function determines if the string is a palindrome.
It finds the middle in the string and from the middle it goes to
the left and to the right one index at a time and compares chars at
the left and at the ridht from the middle. If they match then the
string is the palindrome.
*/
bool Pstring::isPalindrome()
{
   bool pal = true;     //indicates if string is palindrome
  
   int start_r;         //right index to go to the end of the string
   int start_l;         //left index to go to the begining of the string
  
   //if string has even number of chars
   if (length() % 2 == 0)
   {
       start_r = (this->length()) / 2;          //set right index
       start_l = start_r - 1;                   //set left index
   }
   else
   {
       start_r = ((this->length()) / 2) + 1;        //set right index
       start_l = ((this->length()) / 2) - 1;        //set left index
   }
   //iterate until mismatch found or the end of the string reached
   while (pal && start_r < this->length())
   {
       //if chars at these locations are not equal set pal to false
       if ((*this)[start_l] != (*this)[start_r])
       {
          
           pal = false;
       }
       start_l--;     //decrement left index
       start_r++;     //increment right index
   }
  
   return pal;
}

Pstring.h

#ifndef PSTRING_H
#define PSTRING_H

#include <iostream>
#include <string>
using namespace std;

class Pstring: public string
{
public:
   Pstring(string s) : string(s) { }
   int len() { return this->length(); }
   bool isPalindrome();
private:

};

#endif