DSA/stringispalindromeornot.cpp at main · Hrishi75/DSA · GitHub

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#include<iostream>

using namespace std;

// bool isPalindrome(string s) {

//         int left = 0, right = s.length()-1;
//         while(left<right)
//         {
//             if(!isalnum(s[left]))
//                 left++;
//             else if(!isalnum(s[right]))
//                 right--;
//             else if(tolower(s[left])!=tolower(s[right]))
//                 return false;
//             else {
//                 left++;
//                 right--;
//             }
//         }
//         return true;

// }
// int main() {

//   string str = "ABCDCBA";
//   bool ans = isPalindrome(str);

//   if (ans == true) {
//     cout << "Palindrome";
//   } else {
//     cout << "Not Palindrome";
//   }
//   return 0;
// }

//recursive method

bool palindrome(int i, string& s){

    // Base Condition
    // If i exceeds half of the string means all the elements
    // are compared, we return true.
    if(i>=s.length()/2) return true;  //quotient

    // If the start is not equal to the end, not the palindrome.
    if(s[i]!=s[s.length()-i-1]) return false;

    // If both characters are the same, increment i and check start+1 and end-1.
    return palindrome(i+1,s);
}

int main() {

	// Example string.
	string s = "madam";
	cout<<palindrome(0,s);
	cout<<endl;
	return 0;
}