Thread: Palindrome program not working

  1. #1
    Registered User
    Join Date
    Mar 2017
    Posts
    13

    Question Palindrome program not working

    What I'm trying to do is check if a string is a palindrome or not. I'm supposed to ignore all non-letter characters but it doesn't appear to be working. Any suggestions?

    For ex. When I type in "He lived as a devil, eh?" it tells me that it's not a palindrome even though it is.

    Code:
    #include <iostream>
    #include <string>
    #include <cctype>
    
    
    using namespace std;
    
    
    int main()
    {
        char ch;
        string s;
        cin.get(ch);
        while (ch!='\n')
        {
            if(ispunct(ch) || isspace(ch) || isdigit(ch))
            {
                ch='\0';
            }
            else
            ch=tolower(ch);
            s+=ch;
            cin.get(ch);
        }
    
    
        if(s==string(s.rbegin(),s.rend())){
            cout<<s<<"\nis a palindrome.";
        }
        else
            cout<<s<<"\nis not a palindrome.";
    
    
        return 0;
    }

  2. #2
    Banned
    Join Date
    Aug 2017
    Posts
    861
    I had to look that up ,,

    Palindrome, Palindrome Words List, Longest Examples, Define Palindrome

    Palindrome List – Palindromes, Palindrome Words, Examples

    so what is the basis of comparison to find one? Because by taking a 'd' it says it is, then by using an example in that list I get nope.
    Code:
    userx@slackwhere:~/bin
    $ ./temp
    d
    d
    is a palindrome.userx@slackwhere:~/bin
    $ ./temp
    A car, a man, a maraca.
    helloacaramanamaraca
    is not a palindrome.userx@slackwhere:~/bin
    $
    Plus you have no lead in message telling the user what to do. If I did not read the code and what you said to do in your explanation in here then I'd be lost.

    id try flipping your if else around then run a few more different ones to see what that does.
    Code:
     if(s==string(s.rbegin(),s.rend()))
             cout<<s<<"\nis not a palindrome.\n";
      else     
             cout<<s<<"\nis a palindrome.\n";
    Code:
    userx@slackwhere:~/bin
    $ ./temp
    A car, a man, a maraca.
    acaramanamaraca
    is a palindrome.
    userx@slackwhere:~/bin
    it might be that return value that is causing this effect, I do not know what it is.
    Last edited by userxbw; 11-06-2017 at 10:11 PM.

  3. #3
    Lurking whiteflags's Avatar
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    9,616
    You are still inserting characters you don't want they are just all \0 now. It would be better to not insert them at all.
    Last edited by whiteflags; 11-06-2017 at 10:24 PM.

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