Question

A palindrome is a sequence that is equivalent to its reverse. Write a recursive function that determines if A[i], ..., A[j] is a palindrome.

Answer 1

Answer:

#include <stdio.h>  

#include <string.h>  

#include <stdbool.h>  

// A recursive function that  

// check a str[s..e] is  

// palindrome or not.  

bool isPalRec(char str[],   int s, int e)  

{  // If there is only one character  

   if (s == e)  

   return true;  

  // If first and last  

   // characters do not match  

   if (str[s] != str[e])  

   return false;  

   // If there are more than  

   // two characters, check if  

   // middle sub-string is also  

   // palindrome or not.  

   if (s < e + 1)  

   return isPalRec(str, s + 1, e - 1);  

   return true;  

}    

bool isPalindrome(char str[])  

{  

int n = strlen(str);    

// An empty string is  

// considered as palindrome  

if (n == 0)  

   return true;  

return isPalRec(str, 0, n - 1);  

}    

// Driver Code  

int main()  

{  

   char str[50];  

   scanf("%[^\n]", &str);

 

   if (isPalindrome(str))  

   printf("Number is a Palindrome :");  

   else

   printf("Number is not a Palindrome : " );  

 

   return 0;  

}