Question & Answer: A palindrome is any word, phrase, or sentence that reads the same forward and backward……

A palindrome is any word, phrase, or sentence that reads the same forward and backward.

Here are some well known palindromes:

Able was I, ere I saw Elba

A man, a plan, a canal, Panama

Desserts, I stressed

Kayak

Write a bool funcion that uses recursion to determine if a string arguement reads the

same forward and backward. Demonstrate the function in a program.

Expert Answer

 

C++ Code:

#include <iostream>
#include <string>

using namespace std;

//Function that checks whether string passed is a Palindrome or not
bool isPalindrome(string str, int startPos, int endPos)
{
//Base Condition
if(startPos >= endPos)
{
return true;
}

    //If current character is not an alphabet
if(!isalpha(str[startPos]))
{
//Updating start position
startPos += 1;

        //Recursive call
return isPalindrome(str, startPos++, endPos);
}

    //If current character is not an alphabet
if(!isalpha(str[endPos]))
{
//Updating end position
endPos -= 1;

        //Recursive call
return isPalindrome(str, startPos, endPos–);
}

    //If the characters are not same
if(tolower(str[startPos]) != tolower(str[endPos]))
{
return false;
}

    //Updating positions
startPos = startPos + 1;
endPos = endPos – 1;

    //Recursive call
return isPalindrome(str, startPos, endPos);
}

//Main function
int main()
{
string str;

//Reading a string from user
cout << “nn Enter a string: “;
getline(cin, str);

//Checking for palindrome
    if(isPalindrome(str, 0, strlen(str.c_str())-1))
{
cout << “n Is a Palindrome!!!! n”;
}
else
{
cout << “n Is not a Palindrome!!!! n”;
}

cout << “nn”;
return 0;
}

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Sample Run:

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