Stack and Queue Palindrome Program

Question

I am writing a program to determine if a user-entered string of characters is a palindrome. The program compiles, however when output is printed, all strings of characters are determined to be palindromes even if they are not. I read my textbook varies times, reviewed and debugged the code dozens of times, looked at other similar palindrome questions, but I am still lost.

My code is as follows:

 #include <iostream>
    #include <stack>
    #include <queue>
    #include <string>
    using namespace std;

    int main (void)
    {
      stack <char> s;
      queue <char> q;
      string letter;
      int length;

      cout<<"Please enter a series of characters."<<endl;
      getline (cin, letter);
      length = letter.size();

      for (int i=0; i<length; i++)
        {
          q.push(i);
          s.push(i);
        }

         bool isPalindrome = true;
         while (isPalindrome==true && (!s.empty() && !q.empty()))
         {
           if (s.top() != q.front())
            {
              isPalindrome = false;
            }
          else
           {
            q.pop();
            s.pop();
           }
         }

       if(isPalindrome==false && (s.empty() && q.empty()))
         {
          cout<<"True or false: "<<isPalindrome<<endl;
          cout<<"Is not a palindrome."<<endl;
         }
       else
         {
           cout<<"Is a palindrome."<<endl;
         }

    }

I would greatly appreciate if someone could explain why this is happening. Thank you!

Answer 1

Well, for starters, you push integers instead of characters. To push the characters in the string use q.push(letters[i]) instead of q.push(i).

You can also get rid of the stack and push half of the string to the queue and then compare it to the other half. Like this:

#include <iostream>
#include <queue>
#include <string>

using namespace std;

int main (void)
{
  queue <char> q;
  string letter;
  int length;

  cout<<"Please enter a series of characters."<<endl;
  getline (cin, letter);

  bool isPalindrome = false;

  if (letters.size() > 0)
  {
    int length = letter.size() / 2;

    for (int i=0; i<length; i++)
    {
      q.push(letters[i]);
    }

    isPalindrome = true;

    for (int i = 1; i <= length && isPalindrome; ++i)
    {
      isPalindrome = q.front() == letters[letters.size() - i];
      q.pop();
    }
  }

  if(!isPalindrome)
  {
    cout<<"Is not a palindrome."<<endl;
  }
  else
  {
    cout<<"Is a palindrome."<<endl;
  }

  return 0;
}

Or you can actually just avoid heavy data structures for such a simple task and use a simple loop to do this:

bool isPalindrome = false;
int len = letters.size();

if (len > 0)
{
  isPalindrome = true;

  for (int i = 0; i < len / 2 && isPalindrome; ++i)
  {
    isPalindrome = letters[i] == letters[len - i - 1];
  }
}