Question

There’s a simple string manipulation problem where you are required to reverse the words of each line: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=121&page=show_problem&problem=424

So:

I love you.
You love me.
We're a happy family.

Would become:

I evol .uoy
uoY evol .em
er'eW a yppah .ylimaf

Now, I’ve written a simple java solution which looks something like:

BufferedReader file = new BufferedReader(new InputStreamReader(System.in));
String s;
while((s=file.readLine())!=null){
    String[] sr = s.split(" ");
    for(int i = 0; i<sr.length; i++)
        System.out.print(new StringBuffer(sr[i]).reverse() + (i==sr.length-1?"\n":" "));
}

Because I am trying to learn c++, I’ve also tried writing a c++ solution which looks like:

string s;
while(getline(cin, s)){
    string tmp = "";
    for(int i = 0; i<=s.length(); i++)
        if( i==s.length() || s[i] == ' '){
            for(int j = tmp.length(); j>=0; j--)
                cout << tmp[j];
            if( i == s.length()) cout << endl;
            else cout << " ";
            tmp = "";
        }else
            tmp += s[i];
}

My questions are:

1. The c++ solution returns “wrong answer”, whereas the java one is accepted, why?
2. What improvements, if any, can be made to the c++ solution?

Answer 1

std::string line_string;
while ( getline( std::cin, line_string ) ) {

    // Instead of `split`, read out of a std::istringstream:
    std::istringstream line_stream( line_string );
    std::string word;
    while ( line_stream >> word ) {

        // Use std::reverse instead of a loop:
        std::reverse( word.begin(), word.end() );

        // Always qualify with std:: instead of using namespace std;
        std::cout << word << ' ';
    }
    std::cout << '\n'; // prefer '\n' to std::endl unless you need a flush
}

http://ideone.com/hd3bg

If this doesn’t pass, it’s probably because of the trailing space at the end of each line. Use a Boolean variable to avoid printing space before newline.