Console text command input

// WK Shearer Oct 2012.
// Simple console application, C++.
// Sample command interface, like a receptor for text based adventure game.
// Takes a command, splits it into words, eliminates blanks and spaces, and
// converts the words to upper case for later comparison to verb / noun bank.
#include <iostream>
#include <string>
#include <cctype>
#include <vector>

using namespace std;

int main()
{
    string mystr;
    char search = ' ';
    string sub_str;
    vector<string> words;

    cout << "Enter command: ";
    getline(cin, mystr);
    cout << "Command is " << mystr << endl;
    //cout << mystr.length() << endl;
    size_t i = 0, j = 0;

    for(i = 0; i < mystr.size(); i++)
    {
        if(mystr.at(i) != search)
        {
            sub_str.insert(sub_str.end(), mystr.at(i));
        }
        if(i == (mystr.size() - 1))
        {
            words.push_back(sub_str);
            sub_str.clear();
        }
        if(mystr.at(i) == search)
        {
            words.push_back(sub_str);
            sub_str.clear();
        }
    }
    // clean out any accidental blank words (extra spaces)...
    //cout << "initial words.size() " << words.size() << endl;
    for(i = words.size() - 1; i > 0; i--)
    {
        if(words.at(i) == "")
            words.erase(words.begin() + i);
    }
    //cout << "words.size() after clean up " << words.size() << endl;

    for(i = 0; i < words.size(); i++)
    {
        cout << words.at(i) << endl;
    }

    // Make words upper case
    for(i = 0; i < words.size(); i++)
    {
        for(j = 0; j < words.at(i).size(); j++)
        {
            if(islower(words.at(i).at(j)))
                words.at(i).at(j) = toupper(words.at(i).at(j));
        }
    }

    for(i = 0; i < words.size(); i++)
    {
           cout << words.at(i) << endl;
    }

    return 0;
}