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Question

I need to use a stack and queue to test for a palindrome. The program works fine with one word answers such as racecar. The problem i am having is that i need to ignore space and punctuation so i can test sentences and questions. Any help is appreciated.

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

int main()
{
    bool palindrome = true;
    char character;
    stack<char> stack;
    queue<char> queue;  
    char a;
    char b;

    cout << "Enter a string; press return." << endl;
    cin >> character;


    while (isalpha(character))
    {
        if (isalpha(character))
        {
            character = tolower(character);
        }

        stack.push(character);
        queue.push(character);
        cin.get(character);
    }

    while (!queue.empty())
    {
        a = stack.top();
        b = queue.front();
        stack.pop();
        queue.pop();
        if (a != b)
            palindrome = false;
    }


    if (palindrome)
        cout << "String is a palindrome." << endl;
    else
        cout << "String is not a palindrome." << endl;
    system("pause");
    return 0;
}

Answer 1

Move

stack.push(character);
queue.push(character);

to the if statement, like so:

if (isalpha(character))
{
      character = tolower(character);
      stack.push(character);
      queue.push(character);
}

You are checking whether it's an alpha character, this way, you won't even load the non-letter characters in the stack/queue. If you want to allow using non alpha characters and to just filter them out, consider using while(cin >> character) so it doesn't terminate on the first non-letter char.

Answer 2

You could do something simple like:

while (!queue.empty())
{
    While(isspace(stack.top())
    {
        stack.pop();
    }
    While(isspace(queue.front())
    {
        queue.pop();
    }
    a = stack.top();
    b = queue.front();
    stack.pop();
    queue.pop();
    if (a != b)
        palindrome = false;
}

Reference: http://www.cplusplus.com/reference/cctype/isspace/