/** This program determines if a string is a palindrome. A palindrome is a string (list of characters) that is read the same forward and backward. */ /** More comments can be found at the end of the code.*/ /** HAPPY LEARNING! */ /*************** CODE ************************/ #include #include using namespace std; bool isPalindrome (string); /* see 1 */ int main(){ string mystr; cout << "Enter a string: "; getline (cin, mystr); /* see 2 */ if (isPalindrome(mystr)) /* see 3 */ cout << mystr << " is a palindrome \n"; else cout << mystr << " is not a palindrome \n"; } bool isPalindrome(string str){ int length = str.length(); if(length <= 1) /* see 4 */ return true; if(str[0] == str[length-1]) /* see 5 */ return isPalindrome(str.substr(1, (length - 2))); return false; /* see 5 */ } /*************** COMMENTS ********************/ /* 1. Function declaration. A function needs to be declared before being used. The function definition can be found after main() */ /* 2. These three lines of code allow the user to input a string. */ /* 3. If isPalindrome returns true, print "is a palindrome, otherwise print "is not a palindrome" */ /* 4. An empty string or a string with one character are palindromes by definition, so we return true. */ /* 5. If the first and the last character are the same then we can remove these two characters and verify that the rest of the string is also a palindrome. We accomplish this by calling the same function again with the new parameter. This is the recursive step.*/ /* 6. If both previous conditions fail then the string is not a palindrome therefore we return false.*/

Check if string is a palindrome - using recursion