Extracting numbers from from a user input and comparing it to

[Andrew Albers]

i personally cannot get lines 22-26 to do what they are supposed to do. It is supposed to reverse the guess and random number (ex: 123 = 321). Im just looking for a little bit of help on those lines. thankyou.

 
import java.util.Scanner;

public class Lottery
{
	public static void main(String[] args)
	{
	//Generate random lottery numbers
	int lottery = (int)(Math.random() * 1000);
	System.out.printf("%d" , lottery);

	//Create Scanner
	Scanner input = new Scanner(System.in);
	System.out.print("Enter your lottery pick (three digits): ");
	int guess = input.nextInt();

	//Determine whether or not the entered guess is some kind of match
	if(guess == lottery)
		{
		System.out.println("Exact mactch: you win $10,000");
	}

	else if (guess % 100 == lottery % 100 &&
			 guess % 10 == lottery % 10 &&
			 guess / 100 == lottery / 100 &&
			 guess / 10 == lottery / 10)
			 {
			 System.out.println("Match all digits: you win $3,000");
	}

	else if (guess / 100 == lottery / 100 ||
			 guess % 100 == lottery % 100 ||
			 guess / 10 == lottery / 10 ||
			 guess % 10 == lottery % 10 ||
			 guess % 100 == lottery % 100 ||
			 guess / 100 == lottery / 100 ||
			 guess % 10 == lottery % 10 ||
			 guess / 10 == lottery / 10)
			 {
		System.out.println("Match one digit: you win $1,000");
	}

	else {
		System.out.println("Sorry, no match");
		}
	}
}   

[Henry Wong]

else if (guess % 100 == lottery % 100 &&   
             guess % 10 == lottery % 10 &&   
             guess / 100 == lottery / 100 &&   
             guess / 10 == lottery / 10)   
             {   
             System.out.println("Match all digits: you win $3,000");   

The first line of the condition checks to see if the units and the tens digits are equal. The second line checks to see if the units digit are equal. This makes the second line moot, as any test that will pass the first line will also pass the second line.

The third line of the condition checks to see if the hundreds digit and higher are equal. The fourth line checks to see if the tens digit and higher are equal. This makes the third line moot, as any test that will pass the fourth line will also pass the third line.

And finally, to pass both the first and fourth lines, the two numbers must be the same. This makes the whole condition moot, as we know the numbers are not exactly equal, as it would not have arrived at this "else" clause if they were equal.

Henry

[Rob Spoor]

Basically, you would need a better way to check if one digit is in another number:

public boolean digitIsInNumber(int digit, int number)
{
    // assumption: digit is between 0 and 9 inclusive
    while (number > 0)
    {
        if (digit == number % 10) return true; // matches the last digit
        number = number / 10; // cut off the last digit
    }
    return false;
}

You would then have to call this method for each of the digits in your number:

if (digitIsInNumber(guess % 10, lotto) &&
    digitIsInNumber((guess / 10) % 10, lotto) &&
    digitIsInNumber(guess / 100, lotto))
{
    ....
}

This check will still fail though, if either the guess or the lotto has duplicate digits and there is a match like that. For instance, if the lotto number is 123 and the guess is 111, then you still have a problem - 1 is in the lotto number. Checking both ways (digitIsInNumber(lotto % 10, guess)) will also not solve this; just check with lotto 112 and guess 122.

You could try sorting the digits within the number, and then check if the sorted values are equal:

// helper method; this goes outside the method of course
public int sortDigits(int number)
{
    // assumption: number is between 0 and 999, inclusive
    int[] array = {number % 10, (number / 10) % 10, number / 100};
    java.util.Arrays.sort(array);
    int sorted = array[0] + 10 * array[1] * 100 * array[2];
    return sorted;
}

// call them
int sortedLotto = sortDigits(lotto);
int sortedGuess = sortDigits(guess);
if (sortedLotto == sortedGuess)
{
    // the same digits, even with the same count of each. So 111 will not match 123, but 321 will because it will be sorted to 123
}

That brings us to one small flaw in your logic: you never check if the user input is in the right range.

[Andrew Albers]

thank you very much for the help.