#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main()
{
   // (1) Read an integer from the user
    int n;
    cout << "Enter n (must be odd and in range [3,39]): ";
    cin >> n;

   // (2) Check to see if it's not valid
   // (3) If not valid, read an integer from the user again
   //        and loop back up to step (2)
    // while n is less than 3 OR n is greater than 39
    //           OR n is an even number
    while ( n < 3  ||  n > 39  ||  n % 2 == 0  )
    {
        cout << "Nope.  Invalid.  Try again: ";
        cin >> n;
    }

    cout << "Hey, thanks, that's a valid input.\n";

    // the above code is an example of
    //    input validation


    char letter = 'P';
    string word = "computer";

    cout << letter << endl;
    cout << word << endl;
    cout << word[3] << endl;

    for ( unsigned int i = 0 ; i < word.length() ; i++ )
    {
        cout << "Character at index " << i
             << " is " << word[i] << endl;
    }

    cout << "Enter a single word: ";
    cin >> word;
    // cin will read characters until it
    //   encounters a space (' ' or '\t')

    cout << "You entered " << word << '.' << endl;

    cin >> word;
    cout << "Then you entered " << word << '!' << endl;


    // ignore the next set of characters
    //   until we see a '\n' character
    // ignore a maximum of 1000 characters
    cin.ignore( 1000, '\n' );

    cout << "Entire a sentence:" << endl;
    string line;
    getline( cin, line );
    // getline() reads an entire line of input
    //   (not including the '\n') and stores
    //   the entire string in the line variable

    cout << "You typed in: " << line << endl;

    if ( isalpha( line[0] ) )  // this is from <cctype>
    {
        cout << "The first char you typed is a letter.";
        cout << endl;
    }

    if ( isupper( line[0] ) )
    {
        cout << "First char is UPPERCASE letter\n";
    }

    // isalpha()  isupper()  islower()
    // isdigit()  isspace()  ispunct()

    // Write a for loop to print the line variable
    //   in reverse
    for ( int i = (int)line.length() - 1 ; i >= 0 ; i-- )
    {
        cout << line[i];
    }
    cout << endl;

    // Write a for loop to print each lowercase letter
    //   in the line variable (i.e. skip all others)
    for ( int i = 0 ; i < (int)line.length() ; i++ )
    {
        if ( islower( line[i] ) ) {
            cout << line[i];
        }
    }
    cout << endl;


    return 0;
}