Exercise 5.10 (ACCELERATED C++)

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Hi, I don't know how to stop the message "The longest palidrome is" from appearing if the user doesn't enter anything (just entering EOF). Where should I put that phrase? I'm not sure enough about the meaning of try-catch stuff. Thanks a lot...

Code:

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/*
        Write a program to (1) find all the palindromes in a dictionary and (2) find the longest palindrome
*/
#include <iostream>
#include <string>
#include <vector>
#include <stdexcept>
#include <algorithm>
using namespace std;

vector<string> read_words(string&);
bool found(const string&);

int main()
{
        cout << "Enter some words: " << endl;
        string s;
        try {
                vector<string> myvec = read_words(s);
                vector<string>::iterator it = myvec.begin();
                while (it != myvec.end()) {
                        if (found(*it)) {
                                cout << *it << " ";
                                ++it;
                        }
                        else {
                                it = myvec.erase(it);
                        }
                }
                cout << endl;
                cout << "The longest palidrome is ";
                string::size_type maxlen = 0;
                string longest;
                for (int i = 0; i != myvec.size(); ++i) {
                        if (myvec[i].size() > maxlen) {
                                maxlen = max(maxlen, myvec[i].size());
                                longest = myvec[i];
                        }
                }
                cout << longest << endl;

        } catch (domain_error e) {
                e.what();
        }

        return 0;
}

vector<string> read_words(string& s)
{
        vector<string> v;
        while (cin >> s)
                v.push_back(s);

        typedef vector<string>::size_type vec_sz;
        vec_sz size = v.size();
        if (size == 0)
                throw domain_error("Empty vector");

        return v;

}

bool found(const string& s)
{
        bool found = true;
        for (string::const_iterator i = s.begin(), j = s.end() - 1; i < j; ++i, --j) {
                if (*i != *j)
                        found = false;
        }
        return found;
}

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If the user enters no text, but an immediate EOF, the line "The longest palindrome is: " is not printed. If you change your catch to be

Code:

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cout << e.what();

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then you'll see "Empty vector" printed instead.