Problem with number arrangement :(

[Amit Raj Ps]

i am trying to execute a program with the following number arrangement.

3 2 1
3 2
3

i have used "i" for rows and j for columns.

class Demo
{
public static void main(String [] args)
{
for(int i=1; i<=3; i++)
{
for(int j=3; j>=1; j--)
{
if(i+j<=4)
{
System.out.print(j);
}
else
{
System.out.print(" ");
}
}
System.out.println();
}
}
}

The output i got is

D:\Amit\Java\New folder>javac Demo.java

D:\Amit\Java\New folder>java Demo
321
21
 1

i spoke to my trainer regarding the same, and he told me to swap j with space and vice versa.

class Demo
{
public static void main(String [] args)
{
for(int i=1; i<=3; i++)
{
for(int j=3; j>=1; j--)
{
if(i+j<=4)
{
System.out.print(" ");
}
else
{
System.out.print(j);
}
}
System.out.println();
}
}

}

The new output i got is:

D:\Amit\Java\New folder>javac Demo.java

D:\Amit\Java\New folder>java Demo

3
32

The second code doesn't make much of a sense, since i have used the if condition to print a integer when i+j<=4,  or else use space.

Would really appreciate your help, thank you.

[Omkar Shetkar]

Inner for loop needs to be checked.

It is more to do with logic than Java.

public class Demo {
   public static void main(String[] args) {
       for (int i = 1; i <= 3; i++) {
           for (int j = 3; j >= i; j--) {
//                if (i + j <= 4) {
               System.out.print(j + " ");
//                } else {
//                    System.out.print(" ");
//                }
           }
           System.out.println();
       }
   }
}

Of course, you can think of how to remove extra space appended at the end of each line.  

[Amit Raj Ps]

 

Omkar Shetkar wrote:Inner for loop needs to be checked.

It is more to do with logic than Java.

public class Demo {
   public static void main(String[] args) {
       for (int i = 1; i <= 3; i++) {
           for (int j = 3; j >= i; j--) {
//                if (i + j <= 4) {
               System.out.print(j + " ");
//                } else {
//                    System.out.print(" ");
//                }
           }
           System.out.println();
       }
   }
}

Of course, you can think of how to remove extra space appended at the end of each line.  

Thanks for the reply, can you please explain the meaning of " for (int j = 3; j >= i; j--) " and S.O.P(j + " ") , there are few program executed in my class with j>=i , having hard time understanding the logic.

I have asked couple of my friends , to make me understand the j>=i , all failed to make me understand the logic

[Omkar Shetkar]

To understand the meaning of this program, better take pen and paper.
Write down the control flow of the program.

For eg,
------------------
i                  j
------------------
1                 3
                  2
                  1
                      <-- Now j >=i is TRUE, hence skips inner loops
2                 3
                  2
                     <-- Now j >=i is TRUE, hence skips inner loops
3                 3
                     <-- Now j >=i is TRUE, hence skips inner loops
                 


Console
-----------
3 2 1
3 2
3


This way you can understand a computer program and its logic.

[Amit Raj Ps]

 

Omkar Shetkar wrote:To understand the meaning of this program, better take pen and paper.
Write down the control flow of the program.

For eg,
------------------
i                  j
------------------
1                 3
                  2
                  1
                      <-- Now j >=i is TRUE, hence skips inner loops
2                 3
                  2
                     <-- Now j >=i is TRUE, hence skips inner loops
3                 3
                     <-- Now j >=i is TRUE, hence skips inner loops
                 


Console
-----------
3 2 1
3 2
3


This way you can understand a computer program and its logic.

WoW thanks a lot Omkar, you made it look so easy. Now i know what exactly it means ( kinda slow learner) .
However, when i tried to execute the code which you have given, it worked like a charm. But when i tried to give spacing, i hit a road block again. Can you tell me what am i doing wrong. And sorry for being such a pain

public class Demo
{
public static void main(String[] args)
{
       for (int i = 1; i <= 3; i++)
{
            for (int j = 3; j >= i; j--)
{
if (i + j <= 4)
{
              System.out.print(j + " ");
                }
else
{
                  System.out.print(" ");
            }
            }
            System.out.println();
        }
    }
}

this is the output i am getting

D:\Amit\Java\New folder>java Demo
3 2 1
2

[Omkar Shetkar]

I would say write the logic again on pen and paper to figure out the issue.
This will surely will give you a clue.
To give you some hint, you want to have SPACE only when j is less than i.