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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:
