CODEWITHSUNDEEP
c++stackqueuepalindrome
user3020033
user3020033

Reputation: 15

Palindrome detector using stacks and queues C++

I am working on palindrome detector in C++ that reads in a file and marks the lines that are palindromes with the indicator "*". Here's what I have.

PalindromeDetector::PalindromeDetector(const string& iFile, const string& oFile) {
myInFile = iFile;
myOutFile = oFile;
}

void PalindromeDetector::detectPalindrome() {
    ifstream fin(myInFile.data());
    ofstream fout(myOutFile.data());
    string nLine, palLine;
    while (getline(fin, nLine)){
        if (isPalindrome(nLine)){
            fout << nLine << " ***";
        } else {
            fout << nLine;
        }
    }
    fin.close();
    fout.close();
}

bool PalindromeDetector::isPalindrome(const string& str) {
    Stack<char> charStack(1);
    ArrayQueue<char> charQueue(1);
    char ch1, ch2;
    for ( unsigned i = 0; i < str.size(); i++){
        if (isalnum (str[i])){
            tolower(str[i]);
            try {
                charStack.push(str[i]);
                charQueue.append(str[i]);
            } catch ( StackException& se ){
                charStack.setCapacity(charStack.getCapacity() * 2);
                charQueue.setCapacity(charQueue.getCapacity() * 2);
                charStack.push(str[i]);
                charQueue.append(str[i]);
            }
        } else {
            while ( !charStack.isEmpty() || !charQueue.isEmpty() ){
                ch1 = charStack.pop();
                ch2 = charQueue.remove();
                if ( ch1 != ch2 ){
                    return false;
                }
            }
        }
    }
    return true;
}

I'm having 2 problems with this so far: 1. It isn't correctly outputting the file with the "*" at the end of the line; it's doing it at the front for some reason. 2. It only marks the first line in each block of the file, not the lines that are palindromes. I would really appreciate some help on this.

Upvotes: 0

Views: 1332

Answers (1)

Ed Heal
Ed Heal

Reputation: 60037

Why are you making isPalidrome so complicated?

Could be done as thus

bool isPalidrome(const string &s) {
    int left = 0;
    int right = s.length() - 1;
    while (left < right) {
       if (s[left] != s[right]) return false;
       left++; right--;
    }
    return true;
}

Of course you might what to add case-insensitivity

EDIT

Using the more silly way of stacks and queues

bool isPalidrome(const string &s) {
   // Put everything on both
    std::stack<char> lifo;
    std::queue<char> fifo;
    unsigned int loop;
    for (loop = 0; loop < s.length); ++loop) {
      lifo.push(s[loop]);
      fifo.push(s[loop]);
    }
    // Note stack and queue the characters are in reverse order from each other
    for (loop = 0; loop < s.length); ++loop) {
       if (lifo.pop() != fifo.pop()) return false;
    }
    return true;
}

Upvotes: 2

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