CodeGym/Help with Java Tasks/My program does its job, but JUDGE won't validate it.

Level 31

13.07.2022
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My program does its job, but JUDGE won't validate it.

Question about the task

Second smallest number entered

Java Syntax, Level 4, Lesson 5

Under discussion

Hi guys, pls gimme a hint.

In this task, you need to:

Read integers from the keyboard until something else is entered, such as a string or a character.
At least two numbers must be entered. If less than two integers are entered, then terminate the program with an error. You don't need to handle this situation.
Display the second smallest integer entered from the keyboard. If several such numbers are entered, you must display any of them.
There may also be several minimum numbers.

Example input:

8

4 // Minimum number

7

4 // Minimum number

5 // Second smallest number

9

5 // Second smallest number

exit

Example output:
5

Requirements:

The program should read numbers from the keyboard.
The program should display a number on the screen.
The program should display the second smallest integer entered.
If several second smallest numbers are entered, then you need to display any one of them.
You need to read data from the keyboard in a while loop.

package en.codegym.task.pro.task04.task0410; import java.util.Scanner; /* Second smallest number entered */ public class Solution { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); int min = Integer.MAX_VALUE; int max = Integer.MIN_VALUE; while (scanner.hasNextInt()){ int x = scanner.nextInt(); if ( x < min ) { min = x; } else { max = x; } } if (min < max){ min = max; } System.out.print(min); } }

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Alex Tor Software Developer

13 July 2022, 15:30

Thank you very much guys, I highly appreciate your participation in this thread and the efforts you've done. The task hasn't been resolved yet, but I believe I'm about to solve it, here is my last try: The third requirement is left to be met.

public static void main(String[] args) throws InputMismatchException {
        Scanner scanner = new Scanner(System.in);
        int firstMin = Integer.MIN_VALUE;
        int secondMin = Integer.MIN_VALUE;
        String str = "";
        while (scanner.hasNextInt()) {
            int first = scanner.nextInt();
            if (!scanner.hasNextInt()) {
                str = scanner.nextLine();
                break;
            } else {
                int second = scanner.nextInt();

                if (first <= second) {
                    firstMin = second;
                    secondMin = first;
                    break;
                } if (first >= second){
                    firstMin = first;
                    secondMin = second;
                } else {
                    secondMin = first;
                }
            }
        }
        System.out.println(secondMin);
    }
}

Thomas

Level 41 , Bayreuth, Germany

13 July 2022, 16:12

don't read more than one input from the console in each iteration of the loop. lines 14-16 were perfect in your original code. Then start checking if the input x is < than min. If so set x to min and min to secondMin. else check if x < secondMin && x != min ... if so secondMin = x Just add some code to check if there are more than two numbers entered... that's it. I've coded that program now and I started with 4 ints

int     min = Integer.MAX_VALUE,
        secondMin = min,
        count = 0,
        input;

while (scanner.hasNextInt()) {
    input = scanner.nextInt();
    count++;

    // here what I described above
}
if (count > 1)
    System.out.print(secondMin);
else
    System.out.println("You need to input at least two numbers");

I think CG does not check other inputs than at least two numbers so the else output probably won't harm. If not... remove it

Guadalupe Gagnon

Level 37 , Tampa, United States

13 July 2022, 16:13

#1 from the conditions: At least two numbers must be entered. If less than two integers are entered, then terminate the program with an error. You don't need to handle this situation. It says this program MUST have 2 numbers entered in the very beginning. This would be logical to have them entered prior to the loop. If something other than a number is entered for those 2 then the program should end with an error. The code you shared still does not do this. When I entered one or no numbers it still outputs -2147483648. #2 This code now only works when entering 2 numbers at a time. Anytime I enter an odd amount of numbers the loop breaks because of line 8 and the previously entered number is lost. For example, if I entered: 3 2 1 *end* The entered 1 would be read in at line seven and then line 8 would be true because of the entered *end* and the 1 would be lost. #3 'firstMin' is never used. You could remove lines 3, 15, 19 with no effect to the code. Looking at the algorithm it would seem this is to save the value minimum entered number up until that point. Since it isn't being used that way there are logical errors in the algorithm. #4 Line 17 is breaking the loop if the number entered for line 12 is greater than the number entered for line 7.

Guadalupe Gagnon

Level 37 , Tampa, United States

13 July 2022, 16:34

Hi Thomas, It needs to end in an error if less than two numbers are entered. That may mean any Exception, though it might also literally mean an Error. So something like this would throw an exception if less than 2 ints are entered without having to bother counting:

int firstMin = scanner.nextInt();
int secondMin = scanner.nextInt();


while(scanner.hasNextInt()) {

}

or you could modify it to this to throw an Error:

int firstMin = 0;
int secondMin = 0;
try {
   firstMin = scanner.nextInt();
   secondMin = scanner.nextInt();
} catch(Exception e) {
   throw new Error();
}

while(scanner.hasNextInt()) {

}

Thomas

Level 41 , Bayreuth, Germany

13 July 2022, 17:02

Hi Lupe, I don't think exceptions are already an issue in level 4. And if you look at the fullfilled requirements that is no problem here. As said before I believe CG does not test this and that's why I didn't bother at all and just output the result if there are at least 2 valid inputs.

Guadalupe Gagnon

Level 37 , Tampa, United States

13 July 2022, 17:06

This is the "pro" quest line though. The conditions specifically state: "At least two numbers must be entered. If less than two integers are entered, then terminate the program with an error. You don't need to handle this situation."

Thomas

Level 41 , Bayreuth, Germany

13 July 2022, 17:11

Yep ;) CG doesn't make a fuzz with that 'requirement'. They test with min 2 valid inputs. That's my understanding of that.

Guadalupe Gagnon

Level 37 , Tampa, United States

13 July 2022, 17:16

I would argue, but I have plenty of experience with questionable codegym conditions/requirements, so you are more than likely correct 😉.

Guadalupe Gagnon

Level 37 , Tampa, United States

13 July 2022, 14:13

useful

#1 The code doesn't throw an exception if less than 2 numbers are entered. #2 This code saves the minimum value of the entries as they are entered, only keeping the current minimum and the previous entered number, until the loop breaks. This results in it determining the minimum number and then comparing it to the very last input, and outputting the minimum of those two. So lets say you entered: 1 2 3 4 5 6 *end* The last number is 6. The code would determine the minimum of the previous numbers (which is 1), compare that to the last of 6, and then output the greater of those two, which is 6 (correct output would be 2). If you entered: 6 4 2 5 3 9 7 *end* The last number is 7 and the minimum of the previous entries is 2, so 2 and 7 are compared and the code outputs 7 (correct output would be 3) So the only case where it works is if the last entered number is the actual second to smallest number. In all other cases it outputs the incorrect result.

Guadalupe Gagnon

Level 37 , Tampa, United States

13 July 2022, 14:31

useful

Some other test cases to consider: 2 *end* (should error out) 1 2 *end* (should output 2) 2 2 *end* (outputs 2) 3 3 2 *end* (outputs 3) 2 2 3 *end* (outputs 3) 1 1 12 5 8 1 10 20 4 1 15 21 *end* (outputs 4) 3 5 6 2 4 3 1 *end* (outputs 2)

Thomas

Level 41 , Bayreuth, Germany

13 July 2022, 11:36

useful

You determine only min and max and not min and second min. That's a little bit more difficult. you need a) min, secondMin = Integer.MAX_VALUE and count = 0 variables. b) Cause you need no error handling just read in the first number as min. c) Then enter the loop as you have it now. d) Read a number and check if it is min, if so make secondMin = min and min the read number e) if the read number is not the new min, then check if the read in number is < secondMin and the read in number is not equal to min, if so -> make secondMin the read number. Doing these both checks is important... just try without and enter the sample sequence and you'll see why f) increment count g) outside the loop output secondMin if count > 1 or you cheat and read everything into an array or list, sort and output the second value Oh, and I have no clue if this will validate as I never have seen these pro tasks before ;)

Marco Kragten

Level 6 , Netherlands

13 July 2022, 13:59

useful

Hi Thomas, You're so close. You need to create a starting point before the while loop starts. So you need to determine this first to give the correct values to your int variables. You need to create your min and max variables with some kind of statement first ;)

Thomas

Level 41 , Bayreuth, Germany

13 July 2022, 14:36

useful

I thought I did that with a and b :) That's what I meant in code

int    min = scanner.nextInt();
        secondMin = Integer.MAX_VALUE,
        count = 1;