Question

In C++, write a stack-based application, assignment7.cpp, which can be used to recognize palindromes (strings spelled identically both backward and forwards). Your program should ignore spaces and punctuation, as well as alpha cases; so, for instance, the string “Madam I’m Adam” counts as a palindrome. You must supply your own push and pop operations. For this exercise (alone) you can use global variables for the stack and the stack pointer. Be sure that your program does not let the user push more than 25 characters. Please add comments.

Answer 1

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

bool is_palindrome(string line) {
    stack<char> s;
    char ch;
    string modified;
    for (int i = 0; i < line.size(); ++i) {
        ch = line[i];
        if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
            modified += (char)tolower(ch);
            s.push((char)tolower(ch));
        }
    }
    for (int i = 0; i < modified.size(); ++i) {
        if (modified[i] != s.top()) {
            return false;
        }
        s.pop();
    }
    return true;
}

int main() {
    string line;
    cout << "Enter a sentence: ";
    getline(cin, line);
    if (is_palindrome(line)) {
        cout << line << " is a palindrome" << endl;
    } else {
        cout << line << " is NOT a palindrome" << endl;
    }
    return 0;
}