// CS2310 Exercise 21
// Chapter 18
//
// Name ____________________________ SSN _______________________
//
// Chapter 18. p1052 - 1
// Use recursion to solve the following problem.
// A palindrome is a string of characters that reads the same forward
// and backward. Write a program that reads in strings of characters
// and determines if each string is a palindrome. Each string is on
// a separate input line. Echo print each string, followed by "Is a
// palindrome" if the string is a palindrome or "Is not a palindrome" 
// if the string is not a palindrome. For example, given the input
// string
//
// Able was I ere I saw Elba
// the program would print "Is a palindrome." In determining whether
// a string is a palindrome, consider uppercase and lowercase letters
// to be the same.

#include <iostream>
#include <string>
#include <cstring>

#define MAXLEN 30

using namespace std;

bool Palindrome(string str) {
	// PRE:
	//		str is assigned and its length >= 1
	// POST:
	//		Return true if str is a palindrome
	//		false otherwise
	int len = str.length();
	char ch1, ch2;

	// Get the first character of the string
	// and convert it to uppercase if necessary
	ch1 = str.c_str()[0];
	if (islower(ch1)) ch1 = toupper(ch1);
	// Get the last character of the string
	// and convert it to uppercase if necessary
	ch2 = str.c_str()[len-1];
	if (islower(ch2)) ch2 = toupper(ch2);

	if (len <= 1)
		// Base case: If the length of the string
		// is less than or equal to 1, then ...
		return // Write the return value here
	else 
		// Write the code for general case: It
		// compares the first half of the string
		// to the second half of the string in
		// flip order -- fold the string at the
		// middle and compare two halves 
		// pairwisely.

		// If the first character is not equal to
		// the last character, then return false;
		// otherwise, compare the remaining pairs
		// in the string using resursive call.

		// Hint: We can use function 
		// substr(fst, lst) to get the substring of 
		// a given string from index fst to lst, 
		// e.g., the substring from index 1 to
		// index len-2 of string str is:
		// str.substr(1, len-2);
}

int main() {
	string str;
	char cstr[MAXLEN];
	cout << "Enter the string (* to quit):";
	cin.getline(cstr, MAXLEN, '\n');
	str = (string) cstr;
	while (strcmp(str.c_str(), "*")) {
		if (Palindrome(str))
			cout << "This is a palindrome" << endl << endl;
		else
			cout << "This is not a palindrome" << endl << endl;
		cout << "Enter the string (* to quit):";
		cin.getline(cstr, MAXLEN, '\n');
		str = (string) cstr;
	}
}