//Palindrome analyzer analyzes a string to see if it reads the same forwards and backwards
//ignoring all punctuation

//uses C++ string objects
#include <cctype>          //enables character functions
#include <iostream>
#include <string>          //header to use C++ strings
using namespace std;
//function returns true if the phrase is a palindrome, ignoring all characters except letters and digits
bool isPalindrome(string phrase);
bool isPalindrome(string s, int left, int right);  //overloaded recursive fcn
string strip(string &phrase);
void convertLower(string &s);

int main()
{
    string phrase;      //input string with possible whitespace
    string stripped;    //string containing only alphanumeric chars.
    cout << "Enter a phrase to analyze ";
    getline(cin, phrase);
    stripped = strip(phrase);    //using a fcn defined in program
   // convertLower(stripped);


    if (isPalindrome(stripped))  //use iterative method
        cout << phrase << " is a palindrome ";
    else
        cout << phrase << " is not a palindrome ";
    cout << endl;


    if (isPalindrome(stripped, 0, stripped.length()-1))   //use recursive methods
        cout << phrase << " is a palindrome ";
    else
        cout << phrase << " is not a palindrome ";
    cout << endl;

return 0;
}

// Determines if a string containing only lower case letters and digits is a palindrome
// Recursive method
bool isPalindrome(string s, int left, int right)
{
    bool flag = true;

    if (left >= right)    //have reached the middle of the string?
        return flag;

    if (s.at(left) == s.at(right))
        flag = isPalindrome(s, left + 1, right - 1);
    else
        flag = false;

    return flag;
}


//Determines if a string containing only lower case letters and digits is a palindrome
//Iterative method
bool isPalindrome(string s)
{
    char left, right;
    for (unsigned k = 0; k < s.length()/2; k++)
    {
        int length = s.length();
        left = s.at(k);
        right = s.at(length -(k+1));        //Fix me!
        if ( left != right )    //compare chars on left and right ends
            return false;
    }
    return true;
}  //end isPalindrome()

//this function takes an input string called phrase and strips it down to letters and digits
//converts to all lowercase and returns the stripped string
string strip(string &phrase)
{
     string copy1;
     for (unsigned i = 0; i < phrase.length(); i++)
     {
         if (isalnum(phrase.at(i)))    //check if the character is a letter or digit
        {
           copy1.push_back(tolower(phrase.at(i)));   //add the alphanumeric char to end of string
        }
     }
     cout << "***" << copy1 << endl;      //debug output
     return copy1;
}

void convertLower(string &s)
{
    for (int k = 0; k < s.length(); k++)
        s.at(k) = tolower(s.at(k));         //at extracts a character from the string
}