Help with a pattern using nested loops (java)

  • Java
  • Thread starter MarcL
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    Java Loops
In summary, the conversation discusses the process of creating a diamond pattern using nested loops in Java. The participants share their code and discuss ways to improve it, particularly for reducing the number of loops needed. They also discuss the challenge of creating a diamond pattern with an even number of rows.
  • #1
MarcL
170
2
Hey so I have to make a pattern in the shape of a diamond as follow:
Code:
  1
 123
12345
 123
  1

So first, I wrote the code without using a variable n as the number of rows ( from an input from the user) but just the constant i = 5 ( I am sorry for the variable names, I made many patterns and this was just trying to get it to work so I didn't mind it as I was going to change everything later)
Code:
public class PatternChose {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int k = 0, h=2, c=0;
          for (int i=1 ; i<=5 ; i++)
           {
            { for (int u=2 ; u >= i ; u--)
                  System.out.print(" ");
                   h--;
             for (int j=1  ; j<= i + k ; j++)
                System.out.print(j);
             for (int w=2 ; w>= i; w--)
                System.out.print(" ");
               
                }
                k++;
                System.out.println();
                if (h<0)
                    break;}
              for (int i =2 ; i>=1 ; i--){
                 { for (int l=3 ; l>+i ; l--)
                     System.out.print(" ");
                    for (int m= 0 ; m <=i - c ; m++)
                      System.out.print( m + 1);
                 }
                 c++;
                 System.out.println();
                 
              }
    }

}

Then, as this gave the output that I first did up there, I tried to do it with a value inputted by a user:

Code:
import java.util.Scanner;public class PatternChose {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int k = 0, h=2, c=0, row=1;
        Scanner userInput = new Scanner(System.in);
        System.out.println("Please input your value");
          int newUserInput = userInput.nextInt();
          for (int i=1 ; i<=newUserInput ; i++)
           {
            { for (int u=newUserInput - row ; u >= i ; u--)
                  System.out.print(" ");
                   h--;
             for (int j=1  ; j<= i + k ; j++)
                System.out.print(j);
             for (int w=2 ; w>= i; w--)
                System.out.print(" ");
               
                }
                k++;
                System.out.println();
                if (h<0)
                    break;}
              for (int i =2 ; i>=1 ; i--){
                 { for (int l=3 ; l>+i ; l--)
                     System.out.print(" ");
                    for (int m= 0 ; m <=i - c ; m++)
                      System.out.print( m + 1);
                 }
                 c++;
                 row++;
                 System.out.println();
                 
              }
    }

}
But, I'm having an issue while trying to use a value from an input. This is because in my first code, I used the space to the left of the numbers to tell when the program to break to then form a lower triangle. However, I do notice a pattern with the space vs. the number of rows but it doesn't seem like I'd be able to code it as the values always change. ( I don't think I'm making very much sense??)

Any pointers of what I should do?
 
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  • #2
Code:
import java.util.Scanner;public class PatternChosen {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int rowsForUpperTriangle = 0,  c=1;
        Scanner userInput = new Scanner(System.in);
        System.out.println("Please input your value");
          int newUserInput = userInput.nextInt();
          int h = newUserInput / 2;
          for (int i=1 ; i<=newUserInput ; i++)
           {
            { for (int u=newUserInput / 2 ; u >= i ; u--)
                  System.out.print(" ");
                   h--;
             for (int j=1  ; j<= i + rowsForUpperTriangle ; j++)
                System.out.print(j);
             for (int SpaceToRight=2 ; SpaceToRight>= i; SpaceToRight--)
                System.out.print(" ");
               
                }
            rowsForUpperTriangle++;
                System.out.println();
                if (h<0)
                    break;}
              for (int i =newUserInput / 2 ; i>=1 ; i--){
                 { for (int l=newUserInput / 2 ; l>=i ; l--)
                     System.out.print(" ");
                    for (int m= 1  ; m <= newUserInput - (2 * c) ; m++)
                      System.out.print( m );
                 }
                 c++;
                 System.out.println();
                 
              }
    }

}

Anyone can tell me how I could reduce this code? I know there are shorter way to code a diamond but this is what I got, which is pretty messy for something so simple I think..
 
  • #3
MarcL said:
Anyone can tell me how I could reduce this code? I know there are shorter way to code a diamond but this is what I got, which is pretty messy for something so simple I think..

Hmmm... that seems like a lot of extra loops and processing. Before changing your code, maybe write down in words what you are trying to accomplish.

It looks like for an input of 5, your desired output is 5 lines each with 5 characters (either spaces or integers)...how many (outer) loops would you expect to need to write 5 lines one at a time? How many (inner) loops would you expect to need to write 5 characters one at a time?
How do things change for an even input (number of rows) like 4?
 

1. What is a nested loop in Java?

A nested loop in Java is a loop that is placed inside another loop. This allows for repetitive tasks to be performed multiple times in a specific pattern.

2. How do I create a nested loop in Java?

To create a nested loop in Java, you can simply place one loop inside another loop. The inner loop will be executed multiple times for each iteration of the outer loop.

3. How do I control the number of iterations in a nested loop?

You can control the number of iterations in a nested loop by using conditional statements such as "if" or "while" within the loop. This will allow you to specify when the loop should stop running.

4. Can I have multiple nested loops in my program?

Yes, you can have multiple nested loops in your program. You can have as many layers of nested loops as needed to achieve the desired pattern or result.

5. Are there any common mistakes to avoid when using nested loops?

One common mistake when using nested loops is forgetting to increment or decrement the control variable, which can result in an infinite loop. It is also important to carefully plan and test your nested loop code to avoid unexpected results.

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