import java.util.ArrayList;
import java.util.Scanner;

/**
 * Solves Problem 19.b of Homework 1. Quoting from the homework:
 * <p>
 * Creates a triangle-shaped sorting network (as discussed in
 * class, using a right-pointing triangle) of a given size. The
 * program reads a single integer n on standard input, ignoring all
 * whitespace. The output is the canonical linear representation of
 * the triangle-shaped sorting network for n inputs.
 *
 * @author Ed Ropple
 */
public class CnetCreateTrisortMain {
    /**
     * Takes a single integer from stdin and generates a trisort of the
     * type explained in class, then outputs it in canonical linear form on
     * stdout.
     *
     * @param args      The command line arguments for the program. Are ignored
     *                  by this program.
     */
    public static void main(String[] args)
    {
        String input = "";

        System.out.println("Enter below a single non-negative integer.");
        System.out.println("Whitespace is ignored, but your number is not");
        System.out.println("checked and will generate an exception.");
        System.out.println("Note that this number is the number of ");
        System.out.println("comparators; i.e. inputting 6 will create a");
        System.out.println("trisort from 0 to 5; for a trisort of comparators");
        System.out.println("0 to 9, input 10. (This value is incidentially");
        System.out.println("the same as the number of elements being sorted,");
        System.out.println("as the requirements state.)");
        System.out.println();

        Scanner s = new Scanner(System.in);
        String foo = "";

        // read from stdin, emerge once given non-whitespace input (thank you,
        // trim function, I love you so)
        while (true)
        {
            System.out.print("> ");
            foo = s.nextLine().trim();

            if (foo.length() < 1)
                continue;
            else
                break;
        }

        int trisortSize = Integer.parseInt(foo);

        ArrayList<ComparatorPair> trisortList = new ArrayList<ComparatorPair>();

        for (int i = trisortSize - 1; i > -1; i--)
        {
//            ArrayList<ComparatorPair> tempTrisortList = new
//                    ArrayList<ComparatorPair>();
            for (int j = 0; j < i; j += 1)
            {
                trisortList.add(new ComparatorPair(j, j + 1));
//                tempTrisortList.add(new ComparatorPair(j, j + 1));
            }
//            System.out.println(tempTrisortList);
        }

        System.out.println();
        System.out.println(Functions.makeCanonicalLinearOutput(trisortList));
    }
}